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Eng. 2021, 9, 42, 14070-14078 ADVERTISEMENT RETURN TO ISSUEPREVResearch ArticleNEXT Journal Logo Solar-Driven Water Splitting at 13.8% Solar-to-Hydrogen Efficiency by an Earth-Abundant Electrolyzer * Joakim Ekspong Joakim Ekspong Department of Physics, Umea University, 901 87 Umea, Sweden More by Joakim Ekspong , * Christian Larsen Christian Larsen Department of Physics, Umea University, 901 87 Umea, Sweden More by Christian Larsen Orcidhttps://orcid.org/0000-0002-2480-3786 , * Jonas Stenberg Jonas Stenberg Department of Physics, Umea University, 901 87 Umea, Sweden More by Jonas Stenberg , * Wai Ling Kwong Wai Ling Kwong Department of Chemistry, Umea University, 901 87 Umea, Sweden Department of Chemistry - Angstrom Laboratory, Uppsala University, 751 20 Uppsala, Sweden More by Wai Ling Kwong Orcidhttps://orcid.org/0000-0002-9732-8867 , * Jia Wang Jia Wang Department of Physics, Umea University, 901 87 Umea, Sweden More by Jia Wang Orcidhttps://orcid.org/0000-0001-8530-8132 , * Jinbao Zhang Jinbao Zhang Department of Chemistry - Angstrom Laboratory, Uppsala University, 751 20 Uppsala, Sweden College of Materials, Fujian Key Laboratory of Advanced Materials, Xiamen University, Xiamen, Fujian 361005, China More by Jinbao Zhang , * Erik M. J. Johansson Erik M. J. Johansson Department of Chemistry - Angstrom Laboratory, Uppsala University, 751 20 Uppsala, Sweden More by Erik M. J. Johansson Orcidhttps://orcid.org/0000-0001-9358-8277 , * Johannes Messinger Johannes Messinger Department of Chemistry, Umea University, 901 87 Umea, Sweden Department of Chemistry - Angstrom Laboratory, Uppsala University, 751 20 Uppsala, Sweden More by Johannes Messinger Orcidhttps://orcid.org/0000-0003-2790-7721 , * Ludvig Edman Ludvig Edman Department of Physics, Umea University, 901 87 Umea, Sweden More by Ludvig Edman Orcidhttps://orcid.org/0000-0003-2495-7037 , and * Thomas Wagberg* Thomas Wagberg Department of Physics, Umea University, 901 87 Umea, Sweden *Email: [email protected] More by Thomas Wagberg Orcidhttps://orcid.org/0000-0002-5080-8273 Cite this: ACS Sustainable Chem. Eng. 2021, 9, 42, 14070-14078 Publication Date (Web):October 13, 2021 Publication History * Received2 June 2021 * Revised23 September 2021 * Published online13 October 2021 * Published inissue 25 October 2021 https://doi.org/10.1021/acssuschemeng.1c03565 Copyright (c) 2021 The Authors. Published by American Chemical Society RIGHTS & PERMISSIONS ACS AuthorChoiceACS AuthorChoiceCC: Creative CommonsCC: Creative CommonsBY: Credit must be given to the creatorBY: Credit must be given to the creator Article Views 514 Altmetric - Citations - LEARN ABOUT THESE METRICS Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days. Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts. 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Share Add toView In * Add Full Text with Reference * Add Description ExportRIS * Citation * Citation and abstract * Citation and references * More Options Share on * Facebook * Twitter * Wechat * Linked In * Reddit PDF (4 MB) Get e-Alerts Supporting Info (1)>>Supporting Information Supporting Information SUBJECTS: * Electrical properties, * Electrodes, * Catalysts, * Evolution reactions, * Materials Go to ACS Sustainable Chemistry & Engineering Get e-Alerts Abstract [sc1c03565_] High Resolution Image Download MS PowerPoint Slide We present the synthesis and characterization of an efficient and low cost solar-driven electrolyzer consisting of Earth-abundant materials. The trimetallic NiFeMo electrocatalyst takes the shape of nanometer-sized flakes anchored to a fully carbon-based current collector comprising a nitrogen-doped carbon nanotube network, which in turn is grown on a carbon fiber paper support. This catalyst electrode contains solely Earth-abundant materials, and the carbon fiber support renders it effective despite a low metal content. Notably, a bifunctional catalyst-electrode pair exhibits a low total overpotential of 450 mV to drive a full water-splitting reaction at a current density of 10 mA cm^-2 and a measured hydrogen Faradaic efficiency of ~100%. We combine the catalyst-electrode pair with solution-processed perovskite solar cells to form a lightweight solar-driven water-splitting device with a high peak solar-to-fuel conversion efficiency of 13.8%. KEYWORDS: * Solar-driven electrolysis * Earth-abundant materials * Nanostructured catalyst * Perovskite solar cells * Cost analysis * * * Synopsis We report a method for sustainable production of hydrogen using Earth-abundant material catalysts driven by solution-processable perovskite solar cells. Introduction ARTICLE SECTIONS Jump To --------------------------------------------------------------------- The ever-increasing energy demand, spurred by an overall global increase in living standards and a larger world population estimated to reach 10 billion people in 2060, in combination with global warming, mandates a fast transition to renewable energy sources. (1) The Sun offers a continuous, albeit intermittent, source of energy, but the direct conversion of solar energy to electricity will not alone solve the energy demand, due to poorly developed electrical grids in large parts of the world and due to the fact that less than 20% of the energy consumption today is in the form of direct electricity. (2) Converting solar energy to transportable hydrogen fuel by solar-driven water electrolysis or photocatalysis are promising routes to lower fossil-fuel dependence, since the stored hydrogen can be used in fuel cells that convert the chemically stored energy back to electricity, with water as the only byproduct. (3-8) Since H[2] has a very high gravimetric energy density, fuel cells are preferable for long distances and heavy transportation over battery-driven vehicles, and several countries are now rapidly developing an infrastructure for fueling vehicles by hydrogen. (9) Besides usage as a high density energy carrier, H[2] can also be used in many industrial applications, such as producing CO[2]-free steel and NH[3]. However, around 95% of all hydrogen is today produced by reforming natural gas and coal gasification, releasing almost 1 Gt CO [2] to the atmosphere every year, with the consequence being that the current hydrogen economy is far from CO[2] neutral. (5,10) Solar-driven water electrolysis thus represents a potentially efficient way for CO[2]-free hydrogen production. Sustainable water electrolysis requires that the anode and cathode catalysts are noble metal free and contain small amounts of other metals in order to lower system costs and facilitate recycling. Using bifunctional catalysts that work for both hydrogen evolution and oxygen evolution is also advantageous since it facilitates upscaling. In alkaline conditions, transition metal oxides, based on Ni, Fe, and Co, have been shown to exhibit low overpotential for the oxygen evolution reaction (OER), in line with the best noble metal oxides RuO[2] and IrO[2], but few examples of such catalysts are reported for the hydrogen evolution reaction (HER), (11) although approaches such as vacancy engineering, (12-15) bimetallic alloying, and addition of phosphides (12,16) have shown to be promising strategies to lower the overpotential for metals toward HER in alkaline conditions. (17,18) In recent years, the best catalyst electrodes are usually supported on rather expensive nickel foams for achieving a high surface-area 3D network that concurrently is stable and relatively active as a catalyst itself. (19) An alternative support is nanostructured, high surface-area carbon, as carbon is abundant, has a high conductivity, and a good ability to anchor nanocatalysts, especially if properly functionalized. (20-22) However, at harsh alkaline conditions, the carbon at the anode is at risk of being oxidized, albeit this risk is lowered for crystalline carbon phases such as graphite or carbon nanotubes. (23,24) Catalysts such as FeNi-layered double hydroxides feature low overpotential for OER and offer better stability than nanoparticles, since a layered structure could assist in protecting the carbon support against direct exposure to the alkaline electrolyte. (25-27) Fe-Ni alloys, however, exhibit rather high overpotential for HER. In this study, we investigate the effects of adding a third transition metal, molybdenum, to the Fe-Ni alloy. Previously, bimetallic transition metal alloys doped with a third high melting-point transition metal have shown good performance for OER, and molybdenum-based materials have in addition shown excellent performance as HER catalysts. (11,17,28-33) Therefore, for further optimizing the performance of NiFe toward OER but also promote HER, molybdenum was added in the NiFe complex. Here, we report on the design of a trimetallic hybrid catalyst, which drives the water-splitting reaction at 10 mA cm^-2 at an overpotential as low as 450 mV. The low overall overpotential allows us to operate our complete water-splitting device, comprising our hybrid catalyst electrodes and two serially connected solution-processed perovskite solar cells, with a high solar-to-hydrogen conversion efficiency (STH) of 13.8%. Results and Discussion ARTICLE SECTIONS Jump To --------------------------------------------------------------------- To achieve our goal of an abundant electrode, we opted to use carbon paper (CP) comprising carbon fibers (with a typical diameter of 10-20 mm) as the starting material. The CP fibers allow for good anchor points for an extremely fine network of nitrogen-doped carbon nanotubes (NCNTs, typical diameter of 20-120 nm). The NCNTs were grown directly on the carbon fibers using chemical vapor deposition for achieving high adhesion and reduced contact resistance. An essential aspect for a well-coated catalyst structure is the high number of adhesion sites on the nitrogen-functionalized carbon nanotubes, which previously has been proven to be beneficial for catalysts anchoring. (20-22) Furthermore, it has been shown that the introduced nitrogen defects in the NCNTs result in an increased electrical conductivity compared to pristine CNTs. (34) This combined support material, consisting of a carbon-based NCNT/CP network, provides a relatively large surface area (70 m^2/g) with good conductivity, stability, and high density of anchoring sites for the metal catalysts. (21) To finalize the catalyst electrode synthesis, a trimetallic NiFeMo catalyst was decorated onto the NCNT/CP support through hydrothermal synthesis (see Experimental Section for details). While NiFe hydroxides have been used as very efficient catalysts for OER previously, Mo oxides have shown near optimal hydrogen adsorption energies and are seen as promising candidates for HER in alkaline electrolytes and also as an OER catalyst. (29,31,32) Therefore, we have added Mo as a third metal in the catalysts to improve the HER activity and still retain or improve the high OER activity of NiFe. The XPS data in Figure S1 show that the Ni:Fe:Mo ratio is 1.1:1.0:0.4 with an oxygen:metal ratio of 2.05:1.00 in agreement with a metal oxide/hydroxide phase for the catalyst. The low-magnification SEM image of the finished catalyst electrode in Figure 1a demonstrates a high yield of nanostructured catalysts and uniformly coated NCNTs throughout the CP substrate. The close-up in Figure 1b shows a single carbon fiber, with a diameter of 15-20 mm, densely covered by thin NCNTs, which are subsequently decorated by a homogeneous layered structure of the NiFeMo catalyst. Figure 1 [sc1c03565_] Figure 1. SEM images of the (a-c) NiFeMo-NF and (d) NiFeMo-NP catalysts. The (a) low magnification image reveals the overall catalyst electrode structure with CP fibers coated with NCNTs which in turn are decorated with the trimetallic NiFeMo catalyst. The close-up on a single CP fiber in (b) reveals the dense coating of NCNTs and a NiFeMo catalyst on the CP. The high magnification image in (c) of a single decorated NCNT on a NiFeMo-NF OER electrode reveals that the NCNT is densely covered with a nanoflake-structured NiFeMo catalyst. (d) The NiFeMo catalyst on the HER electrode has been subjected to a reduction process leading to a structural change from nanoflakes to nanoparticles, NiFeMo-NP. High Resolution Image Download MS PowerPoint Slide In Figure 1c, the high-magnification SEM image of one single NiFeMo-coated NCNT reveals that it exhibits a nanoflake (NF) morphology of NiFeMo metals that are fully covering the NCNT. This conclusion is supported by the energy-dispersive X-ray spectroscopy (EDS) images shown in Figure S2. We also note that the flake-like structure that is densely covering the nanotubes could protect the underlying carbon atoms from being oxidized at the anode during harsh operational conditions. (35) We refer to the NiFeMo/NCNT/CP catalyst electrode configuration as NiFeMo-NF. In order to investigate the role of Mo doping of the NiFe catalysts, we also synthesized a NiFe reference catalyst without any Mo on the NCNT/CP support but which otherwise followed the same synthesis procedure. This synthesis resulted mostly in particle-like NiFe structures covering the nanotubes (see SEM images in Figure S3), meaning that the Mo precursor also is important for achieving a layered nanoflake structure. In order to prepare a HER electrode of seemingly similar metallic composition, the NiFeMo-NF electrode was reduced in Ar:H[2] (95:5) flow at 450 degC for 2 h and thereafter cooled in the same atmosphere before being retrieved. The reduction treatment resulted in a lowering of the total oxygen:metal ratio from 2.05:1.00 to 1.24:1.00 while also promoting reduced oxidation numbers in the metals along with pure metallic states (XPS, Figure S1). Similar reduction methods are commonly employed to activate HER catalysts such as in stainless steel, NiO, and NiMo catalysts, where the reduced material is found more active, as a result of more optimal adsorption energies and higher electrical conductivity. (17,36,37) The nanoflake structures of the NiFeMo-NF catalysts are concurrently transformed into nanoparticle (NP) structures, as highlighted by the SEM images in Figure 1d. The SEM images also reveal that the catalyst particles remain firmly attached to the NCNT network with a homogeneous coverage of the NCNT/CP support, as indicated by the SEM-EDS images in Figure S2. The reduced catalyst electrode is denoted NiFeMo-NP. To evaluate the electrochemical performance of each catalyst separately, 0.2 cm^2 pieces of the electrodes were punched out and connected in three-electrode cell setups with Ag/AgCl and Pt wire as the reference and the counter electrode, respectively. The measurements were performed in 1.0 M KOH with a 2 mV s^-1 scan speed. The performances of the individual NiFeMo-NP electrode in the HER and that of the NiFeMo-NF electrode in the OER are shown in Figure 2a and b, respectively. For comparison, the Mo-free NiFe catalysts anchored on a similar NCNT/CP support, blank NCNT/CP support as well as Pt wire (HER), and IrO[2] on CP (OER) were also measured. We note that for the NCNTs/CP support, there is no background currents at the gas production potentials, which indicates that the electrode is stable and inert at these conditions. Also, here the NiFe catalyst was reduced before HER tests. Figure 2 [sc1c03565_] Figure 2. Electrochemical measurements showing the performance of the NiFeMo-NF and NiFeMo-NP catalyst electrodes for the (a) HER and the (b) OER. (c) Electrochemical measurement of the full water-splitting reaction catalyzed by NiFeMo-NF as the anode and NiFeMo-NP as the cathode. (d) Results from Faradaic efficiency measurements of each catalyst. The triangles correspond to H[2] and the squares to O[2]. The solid lines show the theoretical amount of produced gases at 100% efficiencies. The electrolyte used in all experiments was 1.0 M KOH. High Resolution Image Download MS PowerPoint Slide Alloying NiFe with Mo leads to a significant increase in HER activity as manifested by a lowering of the overpotential needed to reach 10 mA cm^-2 from 250 mV for NiFe/NCNT/CP to 170 mV for NiFeMo-NP. The overpotentials for the noble metal-free hybrid catalyst are in fact only 105 mV higher than that for Pt wire at the same current density. We also note in agreement with our earlier study that the "blank" NCNT/CP support electrodes possess very poor catalytic activity for HER. (21) A Tafel analysis of the voltammetry data (Figure S5a) indicates that the HER for both NiFeMo catalysts proceeds via a Volmer-Heyrovsky pathway, likely with strong hydrogen adsorption manifested by a lack of a linear Tafel region at low current densities in the Tafel plot, and therefore, the Heyrovsky reaction step would be rate determining. (38,39) A low Tafel slope of around 45 mV/dec is identified at low current densities for the Pt reference electrode. At higher current densities, the Tafel slope for all materials increases to 120 mV/dec, which is a general characteristic for metallic catalyst since the hydrogen coverage is then constant. (39) The OER activity of NiFeMo-NF shows a remarkable low potential at 10 mA cm^-2 of only 1.49 V (Figure 2b), which is superior to any of the tested reference materials including IrO[2] and comparable to the state-of-the-art catalysts. (11,40) The small oxidation peak near 1.4 V likely corresponds to an oxidation reaction, similar to a-Ni(OH)[2] to g-NiOOH transformation in pure nickel samples, although the exact origin is currently unclear due to the complexity of the trimetallic alloy. (41-43) It is clear that the addition of NCNTs to the CP increases the electrode surface area, which in turn renders the normalized current density larger than for both Pt and IrO[2] on CP, manifesting the advantage of NCNT to boost the catalytic activity. The Tafel plot for NiFeMo-NF (Figure S5b) is harder to analyze since the oxidation peak is observed at relatively high current densities. Even though, if we extrapolate the current density, an initial Tafel slope of ~30 mV/dec at low current densities that increases to 60 mV/ dec after the oxidation peak and then to 120 mV/dec can be observed, which is consistent with a metal-OOH to metal-OO^- reaction as the rate-determining step in the OER process. (38) However, the reaction mechanism for OER is normally difficult to confirm due to the high complexity. Similar behavior is seen for all tested materials, and the Tafel slopes eventually increase to greater than 300 mV/dec at larger current densities (~100 mA cm^-2). In solar-driven electrolysis, these limitations are not necessarily of importance since the devices usually operate at the lower current densities produced by the solar cells, typically around 10 mA cm^-2. To measure the performance for complete water splitting, the two catalysts were positioned parallel to each other at 1 cm separation. In this two-electrode setup (denoted NiFeMo-NF|NiFeMo-NP), the NiFeMo-NF was the anode and the NiFeMo-NP electrode the cathode. The scanning was done in the negative direction to eliminate any oxidation peaks that might overlap with the Faradaic current at low current densities. In Figure 2c, the polarization curve shows that for the full water-splitting reaction to occur only 1.68 V is required to reach 10 mA cm^-2, which represents a total overpotential of 450 mV for a current density of 10 mA cm^-2. To certify that the measured current corresponds to gaseous production, the Faradaic efficiency (e[H2]) of the system was quantified by membrane-inlet mass spectrometry. A constant current density of 10 mA cm^-2 was applied to each of the catalysts, and the produced gases were measured at certain time intervals (detailed information in Experimental Section). The resulting efficiencies are shown in Figure 2d as solid green triangles (H[2]) and solid green squares (O[2]), while the corresponding black markers represent the quantified amount of produced gases. The Faradaic efficiencies were near 100% for both gases within experimental error. We find that the average molar ratio of hydrogen to oxygen produced in this experiment to be 2.06:1.00, which is close to the expected 2:1 ratio. Using the 100% Faradaic efficiency and the measured total overpotential of 450 mV at 10 mA cm^-2, we can conclude that the NiFeMo-NF|NiFeMo-NP electrode setup is able to produce H[2] with an electric-to-hydrogen conversion efficiency of 73.2% at a production rate corresponding to a current density of 10 mA cm^-2. The stability of the catalysts is important for applicability in real devices, and this was investigated by applying a steady current density of 10 mA cm^-2 while monitoring the evolution of the applied potential of each catalyst electrode over a 10 h test period. We find that the catalyst electrodes are fairly stable as the combined overpotential for the NiFeMo-NF|NiFeMo-NP electrode pair increases from 1.68 to 1.78 V during the first 10 h of operation (Figure S5c), which arises from an overpotential increase of 40 mV for NiFeMo-NF and 60 mV for the NiFeMo-NP, corresponding to an overall performance decrease of 6%. From other studies on similar catalysts, such a decrease in performance, at relatively low current densities and potentials, is usually related to a lowering of the active catalyst surface area due to catalyst migration and catalyst dissolution. (44) We now turn our attention to the solar-driven hydrogen production device. To target the requirements of a low-cost, lightweight, and stand-alone system, we opted to use perovskite solar cells (PSCs) for the power generation. PSCs have recently emerged as potential low-cost competitors to traditional Si-based solar cells, thanks to their solution-based fabrication using only Earth-abundant materials for their active layers and their high solar-to-electric conversion efficiency. (45-47) In addition, the high output voltage of PSCs renders for simpler (i.e., fewer devices connected in series) device configurations for water-splitting operations where a working potential of at least 1.23 V (not including the catalyst overpotentials) is required. (48,49) A schematic of the PSC device structure is presented in Figure 3a. The device consists of a mixed halide FAI:PbI[2]:MABr:PbBr[2] (1:1.1:0.2:0.2 molar ratio) photoactive layer positioned in between a doped spiro-OMeTAD hole transport layer and a compact/mesoporous TiO [2] bilayer for the electron transport. The top Au cathode is in contact with the spiro-OMeTAD hole transport layer, whereas the bottom FTO anode is in contact with the TiO[2] bilayer. The FTO anode is deposited on a glass substrate, which provides mechanical stability. All layers were deposited by solution-based processes, with the exception of the vacuum-deposited Au cathode and FTO anode. The PSC fabrication protocol is detailed in the Experimental Section. Figure 3 [sc1c03565_] Figure 3. (a) Schematic of the perovskite solar cell structure. (b) J-V characteristics of the champion cell under AM1.5 illumination. The device features a large open-circuit voltage of 1.09 V and a high solar-to-electric power conversion efficiency of 19.4%. Additional performance metrics are presented in the inset. High Resolution Image Download MS PowerPoint Slide A total of 116 different PSC devices were fabricated and characterized under AM1.5 illumination, using a shadow mask with an opening of A[PSC] = 0.118 cm^2 to accurately define the illuminated area. Their performance is summarized in the histogram plots in Figure S6, and the narrow distributions of all of the performance metrics indicate a robust fabrication protocol. The current density-voltage (J-V) characteristic for our best performing PSC is shown in Figure 3b, and it features a short circuit current density of J[SC] = 23.4 mA cm^-2 (average J[SC] = 22.6 mA cm^-2), an open circuit voltage of V[OC] = 1.09 V (average V[OC] = 1.05 V), and a solar-to-electric conversion efficiency of PCE = 19.4% (average PCE = 17.5%). A high fill factor FF = 76% (average FF = 73.5%) is the result of the sharp knee-like J-V trace, ensuring that a high operational voltage can be maintained when the illuminated solar cell is driving a load. The J-V data for the PSC (Figure 3b) were matched with the J-V data of the two-terminal NiFeMo-NF|NiFeMo-NP catalyst pair (Figure 2c) in a load line analysis (Figure 4a) in order to predict the performance of a number of connected and complete solar-driven water-splitting devices. Specifically, the calculated solar-generated currents of two-, three-, and four-series-connected PSCs, with a constant total illuminated area of A[PSC], were compared with the calculated catalyst-consuming current of one NiFeMo-NF|NiFeMo-NP catalyst pair, with a varying active electrode area (A[CAT]). The operation point for each configuration is found at the intersection between the PSC and the NiFeMo-NF|NiFeMo-NP catalyst-pair load lines. This analysis reveals that it is preferable to utilize a two-series connected PSC configuration for the complete solar-driven water-splitting device, because of the high V[OC] and FF of the PSC in combination with the low overpotential of the NiFeMo-NF|NiFeMo-NP catalyst pair. Figure 4 [sc1c03565_] Figure 4. (a) Load line analysis of a solar-driven water-splitting device, as derived from measured J-V data of the PSC (Figure 3b) and the NiFeMo-NF|NiFeMo-NP catalyst-pair electrodes (Figure 2c), with the A[CAT]/A[PSC] ratio increasing from 1 to 10, in steps of 1, as indicated by the arrow. The upper-right inset highlights the operation points, found at the intersections between the catalyst and PSC data, in the region between 1.5-1.8 V. (b) Schematic figure of the water-splitting device with the catalyst electrodes powered by two-series connected PSCs. (c) Calculated I[OP], normalized to the total PSC area (A[PSC]), and STH for various configurations of the solar-driven water-splitting device. The configuration of our tested device, using a two-series connected PSC paired with NiFeMo-NF| NiFeMo-NP catalyst electrodes of A[CAT]/A[PSC] = 8.5, is indicated with an open X. (d) Measured I[OP]/A[PSC] and STH during the 10 h long-term operation for our solar-driven water-splitting device under continuous AM1.5 illumination. The inset in (d) shows the same data on a linear time scale. High Resolution Image Download MS PowerPoint Slide From the operating points derived by our load line analysis, we can extract the operating current (I[OP]) which in turn (through the operating current density, I[OP]/A[PSC]) directly reveals the expected solar-to hydrogen conversion efficiency (STH) of our device via eq 1, as described in the Experimental Section. The calculated I [OP]/A[PSC] (left y-axis) and the corresponding STH (right y-axis) are summarized in Figure 4c as a function of the A[CAT]/A[PSC] ratio (i.e., an increase of catalyst area in comparison to the total PSC area). The data are plotted for the two-, three-, and four-series-connected PSCs. We again find that the two-series connected PSC results in the highest performance; specifically, that an I[OP]/A[PSC] > 11 mA cm^-2, corresponding to an STH > 13.5%, is obtained for A[CAT]/A[PSC] > 1. Increasing A[CAT]/A[PSC] to much larger values than 1 result in a very small increase of STH, but with the drawback that the material cost of the catalyst increases. With these predictions at hand, we designed and fabricated a solar-driven water-splitting device comprising a two-series PSC, with a combined A [PSC] = 0.236 cm^2, and a NiFeMo-NF|NiFeMo-NP catalyst-electrode pair with A[CAT] = 2 cm^2, so that A[CAT]/A[PSC] = 8.5. This combination is marked with an open X in Figure 4c and predicts an I[OP]/A[PSC] = 11.2 mA cm^-2, corresponding to an STH = 13.8%. In order to experimentally test this prediction, two high-performance PSCs were electrically connected to the NiFeMo-NF|NiFeMo-NP catalyst-electrode pair, facing each other at a 4-5 mm interelectrode spacing. The catalyst electrodes were submerged into a 1 M KOH electrolyte, after which a constant AM1.5 illumination was directed at the PSCs. This activation of the two PSCs immediately switched on the generation of O[2] and H[2] gases at the catalyst electrodes by water splitting, as made visible by the bubble generation on the NiFeMo-NF|NiFeMo-NP catalyst electrodes (a photograph of the H[2] -producing water-splitting device is shown in Figure S7). The measured initial value of I[OP]/A[PSC] for the water-splitting device is 11.2 mA cm^-2, which corresponds to an STH of 13.8%. These measured numbers are in excellent agreement with the prediction from the load line analysis and demonstrate the validity of our analysis and, most importantly, the functionality of our developed solar-driven water-splitting device. The measured STH efficiency is improved compared to all previous electrolyzers driven by low-cost PSCs that used solely Earth-abundant electrocatalysts but lower compared to the highest performing perovskite/Si tandem devices that uses noble metal electrocatalysts, which reached an initial efficiency of 17% STH. (3,50-54) We note that in a longer perspective, using Earth-abundant electrocatalysts is necessary for sustainable large-scale H[2] production, both for cost-wise and environmental perspectives. (55) The stability of the water-splitting device is displayed in Figure 4 d. A continuous decrease of I[OP]/A[PSC] and STH during the 10 h measurement is observed, after a very short onset period originating from the shutter of the solar test system. Since the NiFeMo-NF| NiFeMo-NP catalyst electrodes alone demonstrate relatively stable operation during such time period (Figure S5c and d), we turn to the PSCs for an explanation. Figure S8 compares the I[OP]/A[PSC] of the solar-driven water-splitting device to the measured J[SC] of a pristine two-series connected PSC during a continuous AM1.5 illumination stress test at short-circuit conditions. The data clearly reveal that the measured reduction in I[OP]/A[PSC] matches the decline of J[SC], implying that the lowered water-splitting performance with time is primarily due to the degradation of the PSCs. We note that the PSCs were operated in ambient atmosphere without encapsulation and that various efforts into stabilizing nonencapsulated PSC devices are ongoing (56-66) but are outside the scope of this study. In addition to lab-scale demonstrations, there is also value in performing relevant cost analysis on the key components early on in development, simply to point out potential limitations and to motivate topics and set targets for future development. We therefore performed a rudimentary cost analysis focusing on the material costs for fabrication of the NiFeMo-NF|NiFeMo-NP catalyst-electrode pair and the PSC in two different scenarios: (i) a lab-scale scenario, with actual high-waste fabrication and actual lab-scale material costs and (ii) a no-waste scenario, with an estimated no-waste fabrication and actual material costs for similar quality materials. The cost analysis for the NiFeMo-NF|NiFeMo-NP catalyst-electrode pair and the PSC in these two scenarios is detailed in Table S2. For the lab-scale fabrication scenario, we use actual material volumes and costs to calculate an enormous cost of $19,100 m^-2 of coated area for the catalyst-electrode pair. The more interesting cost-per-active-area metric for the catalyst (CPA[CAT]) is obtained when the cost per coated m^2 is multiplied with the geometric fill factor (GFF), defined as the ratio between active and coated area. With a GFF = 89% for the lab-scale catalyst, we obtain a lab-scale CPA[CAT] = $21,500 m^-2. Surprisingly, this high cost is mainly due to the high volume of DMF solvent used during the catalyst decoration step. For the PSC, we found an even more extreme cost of $43,400 m^ -2. Considering the low GFF of 18.7%, this results in a cost-per-active-area for the PSC (CPA[PSC]) of $233,000 m^-2. This cost is mainly driven by the high cost of the glass/FTO substrates and the material-inefficient deposition of the expensive spiro-OMeTAD and Au materials. In the no-waste scenario, the material usage is calculated as the minimum amount of material needed to produce the lab-scale device structure by assuming 100% material utilization as well as reuse of solvents in the catalyst decoration step. This aims to investigate the effects of wasteful fabrication steps on the total cost. We find that no-waste fabrication of the catalyst-electrode pair results in a cost reduction of a factor of 35 to a cost of $540 m^-2 of coated area. The main cost driver is now the carbon paper as well as the catalyst precursors (mainly the Ni and Mo precursors). For the PSC, we find a cost reduction of a factor of 130 with a cost of $325 m^-2 of coated area. Here, the glass substrates, the spiro-OMeTAD, and Au are still the main culprits for the PSC. On the basis of these results, we conclude that further development is needed in order to (i) significantly improve the stability of the PSCs and the catalysts, (ii) replace the expensive Au electrodes and glass substrates and develop low-cost alternatives to the spiro-OMeTAD for the PSCs, and (iii) develop solvent-efficient, low-waste, and large-scale fabrication of the PSC and catalysts. We finally note that such development is already ongoing. (56,67-72) Conclusions ARTICLE SECTIONS Jump To --------------------------------------------------------------------- We present the synthesis, characterization, and application of a solar-driven electrolyzer. The trimetallic NiFeMo catalyst takes the shape of nanometer-sized flakes anchored to a fully carbon-based current collector comprising a nitrogen-doped carbon nanotube network, which in turn is grown on a carbon fiber paper support. This catalyst electrode exhibits a low total overpotential for water splitting of 0.45 V at 10 mA cm^-2 and combined with high-performance solution-processed PSCs forms a solar-driven water-splitting device with an impressive initial STH of 13.8%. We highlight that this performance is achieved with exclusively Earth-abundant materials making up the catalyst electrodes and a solar cell structure that is projected to allow for low-cost solution-based processing. Experimental Section ARTICLE SECTIONS Jump To --------------------------------------------------------------------- Catalyst Synthesis Thin films of Ti (10 nm) and Fe (5 nm) were thermally evaporated (Kurt J. Lesker PVD 75) on carbon paper (Sigracet GDL 34 AA). The carbon paper was then placed into a quartz tube (3 cm diameter) and inserted in a CVD chamber for NCNT growth. The thin metal films were reduced into small particles by heating the chamber to 800 degC in an Ar:H[2] (95:5) flow and then further reduced for 15 min with ammonia (25 mL min^-1). The NCNTs were grown at 800 degC with a 120 mL min^-1 flow of Ar:H[2] (95:5) by injecting pyridine with a syringe (NEMSYS) at 10 mL min^-1 for 45 min and then being cooled in Ar. To synthesize NiFeMo-NF, a small piece (1.5 cm x 2 cm) of the coated carbon paper was mixed with a solution containing 6 mL of DMF and a total concentration of 3 mg mL^-1 of Ni(acac)[2], Fe(acac)[3], and MoO[2] (acac)[2] with a molar ratio of 5:1:0.4. The mixed solution together with the carbon paper was then inserted into a Teflon-lined autoclave and heated at 180 degC for 20 h before being cooled at room temperature and washed carefully with milli-Q water. To create NiFeMo-NP, the final material was further reduced by annealing in an Ar:H[2] (95:5) flow at 450 degC for 2 h and being cooled in the same reducing atmosphere before being taken out. The reference sample NiFe-NCNTs were synthesized following the same recipe without adding molybdenum. Material Characterization SEM was performed on a ZEISS Merlin FESEM microscope, and EDS was measured with an Oxford Instruments X-MAX 80 mm^2 X-ray detector at 5 kV. The XRD patterns were recorded with a Panalytical X'pert X-ray diffractometer with Cu Ka radiation (l = 1.5418 A). XPS analyses were done on a Kratos axis ultradelay line detector electron spectrometer using a monochromatic Al Ka source operated at 150 W. Electrochemical Measurements The polarization curves were recorded with linear sweep voltammetry at a scan rate of 2 mV s^-1 in 1.0 M KOH with a potentiometer (Metrohm-Autolab PGSTAT302N, FRA32 M module). For analyzing individual electrodes, a three-electrode cell setup was used with Ag/ AgCl (CHI111-CH instruments) as a reference electrode and a coiled Pt wire (99.999%) as the counter electrode. The voltage was converted into RHE by adding 0.222 V + 0.059 pH (pH 14). All polarization curves were postcorrected from the iR resistance (2 O) measured from electrochemical impedance spectroscopy. The scanning direction was positive for all polarization curves except for the full device setup, where any interfering oxidation is omitted by instead scanning in the negative direction. Faradaic Efficiency Membrane-inlet mass spectrometry (MIMS) was used to quantify the gas product of OER and HER, and its sensitivity toward O[2] and H[2] was calibrated using known amounts of air and a gas mixture of Ar:H[2] (95:5), respectively. The reference and counter electrodes were the Ag/AgCl/1 M KCl and Pt coil, respectively. A gastight electrochemical cell was used to house the WE and RE in the main compartment, which was separated by a glass frit from another compartment that housed the CE. Both compartments contained 1 M KOH as the electrolyte and were purged with N[2] for 1 h prior to measurement. Chronopotentiometry at -10 mA cm^-2 (for HER) or 10 mA cm^-2 (for OER) was performed for 4 h, during which the gaseous aliquots in the headspace of the main compartment were analyzed using MIMS at 30 min intervals. The sum of the gas in the headspace and electrolyte (calculated using Henry's law) (73) of the main compartment yielded the amount of gas product, which was compared with the value calculated from the assumption of perfect charge-to-O[2] (4-electron oxidation) or charge-to-H[2] (2-electron reduction) conversion to obtain the Faradaic efficiency. Perovskite Solar Cell Fabrication Fluorine-doped tin oxide (FTO)-coated glass substrates (7 O sq^-1, Thin Film Devices, USA) were cleaned by 10 min subsequent steps of ultrasonication in detergent (Extran MA01):DI water (volume ratio 1:10), DI water, acetone, and isopropanol. A compact TiO[2] layer was deposited through spray pyrolysis by placing the clean and dry substrates on a hot plate (PZ28-3TD, Harry Gestigkeit) and raising the temperature stepwise to 500 degC. A precursor solution comprising a mixture of 0.2 M titanium isopropoxide (>97.0%, Sigma-Aldrich) and 2 M acetylacetone (puriss >99.5%, Sigma-Aldrich) in isopropanol (IPA, anhydrous 99.5%, Sigma-Aldrich) with a volume ratio of 59.2:205.4:1000 was sprayed at a rate of 14 mL s^-1 using a hand-held airbrush (Art. 17-372, Biltema), operated at p = 20 psi, with a sweeping motion over the substrates at a 15 cm substrate-to-nozzle distance. After spray pyrolysis, the substrates were kept on the hot plate at 500 degC for 30 min for the TiO[2] to crystallize to the rutile phase (final thickness ~30 nm) before slowly cooling to room temperature. A mesoporous TiO[2] was subsequently deposited by first spin-coating (spin speed = 4000 rpm, acceleration = 4000 rpm s^-1, time = 30 s) a 150 mg mL^-1 precursor solution consisting of TiO[2] nanoparticles (DSL 18NR-T, Dyesol) dispersed in isopropanol followed by annealing at 500 degC for 30 min (final thickness ~200 nm). The perovskite solution consists of formamidinium iodide (FAI, Lumtec), methylammonium bromide (MABr, Lumtec), lead iodide (PbI[2], TCI chemicals), and lead bromide (PbBr[2], TCI chemicals) in a 1:1.1:0.2:0.2 M concentration of FAI:PbI[2]:MABr:PbBr[2]. The FAI:PbI [2] and MABr:PbBr[2] were dissolved separately in a mixture of N,N -dimethylformamid (DMF, anhydrous 99.8%, Sigma-Aldrich) and dimethyl sulfoxide (DMSO, anhydrous >99.9%, Sigma-Aldrich) with a volume ratio of 4:1, before they were stirred together at room temperature to form the perovskite solution. The perovskite solution was spin-coated in a N[2]-filled glovebox ([O[2]], [H[2]O] < 1 ppm) using a two-step spin-coating process (step 1: spin speed = 1000 rpm, acceleration = 1000 rpm s^-1, time = 10 s. step 2: spin speed = 4000 rpm, acceleration = 1000 rpm s^-1, time = 30 s), and 65 mL of chlorobenzene (anhydrous 99.8%, Sigma-Aldrich) was quickly dropped onto the spinning substrate when there was 15 s left of step 2. The coated substrates were annealed at 100 degC for 1 h resulting in a uniform dark brown perovskite active layer film with a thickness of ~600-700 nm. The hole transport layer comprised 2,2',7,7'-Tetrakis(N,N -di-p-methoxyphenylamino)-9,9'-spirobifluorene (spiro-OMeTAD, Lumtec) doped by bis(trifluoromethylsulfonyl)-imide lithium salt (Li-TFSI, Sigma-Aldrich), tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt (III) tris(bis(trifluoromethylsulfonyl)-imide) (Co-TFSI, FK209, Dyenamo), and 4-tert-butylpyridine (TBP, Sigma-Aldrich). Li-TFSI and Co-TFSI were separately dissolved in acetonitrile (anhydrous 99.8%, Sigma-Aldrich) to a molar concentration of 2 and 0.5 M, respectively, before being added to form a 70 mM spiro-OMeTAD, 35 mM Li-TFSI, 2.1 mM Co-TFSI, and 231 mM TBP solution in chlorobenzene. The hole transport layer was deposited by spin-coating the solution (spin speed = 4000 rpm, acceleration = 1000 rpm s^-1, time = 30 s) on top of the perovskite layer resulting in a film thickness of ~200 nm. The substrates were then stored in a desiccator with a dry ambient atmosphere for 24 h before the device was finalized with a 70 nm gold electrode, deposited by thermal evaporation (p < 5 x 10^-6 mbar). An FTO/Au electrode overlap of 3 mm x 7 mm defined the active device area. Solar Simulator Measurements The unencapsulated perovskite solar cells were illuminated using a solar simulator (Oriel sol 3A, Newsport, model 940233 A) calibrated with a reference silicon solar cell (Newsport, model 91150 V) to represent AM1.5 irradiance at P[in] = 100 mW cm^-2. The electrical measurements were performed using a Labview controlled source measure unit (Keithley 2420). The illuminated area for each solar cell was restricted with a shadow mask to 0.118 cm^2 and the I-V characteristics were obtained using a forward-to-reverse bias sweep at a 20 mV s^-1 sweep rate. For the solar-driven water-splitting device, two perovskite solar cells (total illuminated active area A [PSC] = 0.236 cm^2) were connected in series and in turn connected to the NiFeMo-NF|NiFeMo-NP catalyst-electrode pair (A[CAT] = 2 cm^2). The catalyst electrodes were submerged in a 1 M KOH aqueous electrolyte at a 4-5 mm spacing. The operating current (I[OP]) was measured in series with the catalyst and the solar cells during illumination, and a 100% Faradaic efficiency (e[H2]) was used when calculating the solar-to-hydrogen conversion efficiency (STH) through [sc1c03565_](1)where E[0,H20] = 1.23 V is the thermodynamic potential for water splitting. Supporting Information ARTICLE SECTIONS Jump To --------------------------------------------------------------------- The Supporting Information is available free of charge at https:// pubs.acs.org/doi/10.1021/acssuschemeng.1c03565. * XPS, SEM, XRD, electrochemical characterization, solar cell performance measurements, PV-driven electrolysis performance measurements, and cost analysis (PDF) * sc1c03565_si_001.pdf (1.92 MB) Terms & Conditions Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/ permissions.html. Author Information ARTICLE SECTIONS Jump To --------------------------------------------------------------------- * Corresponding Author + Thomas Wagberg - Department of Physics, Umea University, 901 87 Umea, Sweden; Orcidhttps://orcid.org/0000-0002-5080-8273; Email: [email protected] * Authors + Joakim Ekspong - Department of Physics, Umea University, 901 87 Umea, Sweden + Christian Larsen - Department of Physics, Umea University, 901 87 Umea, Sweden; Orcidhttps://orcid.org/ 0000-0002-2480-3786 + Jonas Stenberg - Department of Physics, Umea University, 901 87 Umea, Sweden + Wai Ling Kwong - Department of Chemistry, Umea University, 901 87 Umea, Sweden; Department of Chemistry - Angstrom Laboratory, Uppsala University, 751 20 Uppsala, Sweden; Orcidhttps://orcid.org/0000-0002-9732-8867 + Jia Wang - Department of Physics, Umea University, 901 87 Umea, Sweden; Orcidhttps://orcid.org/0000-0001-8530-8132 + Jinbao Zhang - Department of Chemistry - Angstrom Laboratory, Uppsala University, 751 20 Uppsala, Sweden; College of Materials, Fujian Key Laboratory of Advanced Materials, Xiamen University, Xiamen, Fujian 361005, China + Erik M. J. Johansson - Department of Chemistry - Angstrom Laboratory, Uppsala University, 751 20 Uppsala, Sweden; Orcidhttps://orcid.org/0000-0001-9358-8277 + Johannes Messinger - Department of Chemistry, Umea University, 901 87 Umea, Sweden; Department of Chemistry - Angstrom Laboratory, Uppsala University, 751 20 Uppsala, Sweden; Orcidhttps://orcid.org/0000-0003-2790-7721 + Ludvig Edman - Department of Physics, Umea University, 901 87 Umea, Sweden; Orcidhttps://orcid.org/0000-0003-2495-7037 * * * Notes The authors declare no competing financial interest. Acknowledgments ARTICLE SECTIONS Jump To --------------------------------------------------------------------- T.W. acknowledges support from Vetenskapsradet (2017-04862) Energimyndigheten (45419-1), Artificial Leaf Project Umea (Wallenberg). We thank the UCEM, VISP, NanoLab, and XPS-KBC core facilities at Umea University for support. L.E. acknowledges support from Vetenskapsradet (2019-02345, 2017-04380), Energimyndigheten (50779-1) and Olle Engkvists stiftelse. References ARTICLE SECTIONS Jump To --------------------------------------------------------------------- This article references 73 other publications. 1. 1 World Population Prospects 2019, Rev. 1, 2019. United Nations Department of Economic and Social Affairs. https:// population.un.org/wpp/Publications/Files/WPP2019_Highlights.pdf accessed October 2021). Google Scholar There is no corresponding record for this reference. 2. 2 World Energy Outlook 2019, 2019. International Energy Agency. https://www.iea.org/reports/world-energy-outlook-2019 (acessed 2021-08-13). Google Scholar There is no corresponding record for this reference. 3. 3 Li, R. Latest progress in hydrogen production from solar water splitting via photocatalysis, photoelectrochemical, and photovoltaic-photoelectrochemical solutions. Chinese Journal of Catalysis. 2017, 38, 5- 12, DOI: 10.1016/S1872-2067(16)62552-4 [Crossref], [CAS], Google Scholar 3 Latest progress in hydrogen production from solar water splitting via photocatalysis, photoelectrochemical, and photovoltaic-photoelectrochemical solutions Li, Rengui Chinese Journal of Catalysis (2017), 38 (1), 5-12CODEN: CJCHCI ISSN:. (Science Press) A review. Hydrogen prodn. via solar water splitting is regarded as one of the most promising ways to utilize solar energy and has attracted more and more attention. Great progress has been made on photocatalytic water splitting for hydrogen prodn. in the past few years. This review summarizes the very recent progress (mainly in the last 2-3 years) on three major types of solar hydrogen prodn. systems: particulate photocatalysis (PC) systems, photoelectrochem. (PEC) systems, and photovoltaic-photoelectrochem. (PV-PEC) hybrid systems. The solar-to-hydrogen (STH) conversion efficiency of PC systems has recently exceeded 1.0% using a SrTiO3:La,Rh/Au/BiVO4:Mo photocatalyst, 2.5% for PEC water splitting on a tantalum nitride photoanode, and reached 22.4% for PV-PEC water splitting using a multi-junction GaInP/GaAs/Ge cell and Ni electrode hybrid system. The advantages and disadvantages of these systems for hydrogen prodn. via solar water splitting, esp. for their potential demonstration and application in the future, are briefly described and discussed. Finally, the challenges and opportunities for solar water splitting solns. are also forecasted. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2sXktlGrsbg%253D&md5= 75a8111ec9b2f13851d7bc6741c31dad 4. 4 Chu, S.; Cui, Y.; Liu, N. The path towards sustainable energy. Nat. Mater. 2017, 16, 16- 22, DOI: 10.1038/nmat4834 [Crossref], Google Scholar There is no corresponding record for this reference. 5. 5 Dincer, I.; Acar, C. Review and evaluation of hydrogen production methods for better sustainability. Int. J. Hydrogen Energy 2015, 40, 11094- 11111, DOI: 10.1016/j.ijhydene.2014.12.035 [Crossref], [CAS], Google Scholar 5 Review and evaluation of hydrogen production methods for better sustainability Dincer, Ibrahim; Acar, Canan International Journal of Hydrogen Energy (2015), 40 (34), 11094-11111CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.) A review. This paper examines various potential methods of hydrogen prodn. using renewable and nonrenewable sources and comparatively assesses them for environmental impact, cost, energy efficiency and exergy efficiency. The social cost of carbon concept is also included to present the relations between environmental impacts and economic factors. Some of the potential primary energy sources considered in this study are: elec., thermal, biochem., photonic, electro-thermal, photoelec., and photo-biochem. When used as the primary energy source, photonic energy based hydrogen prodn. (e.g., photocatalysis, photoelectrochem. method, and artificial photosynthesis) is more environmentally benign than the other selected methods in terms of emissions. Thermochem. water splitting and hybrid thermochem. cycles (e.g. Cu-Cl, S-I, and Mg-Cl) also provide environmentally attractive results. Both photoelectrochem. method and PV electrolysis are least attractive when prodn. costs and efficiencies are considered. Therefore, increasing both energy and exergy efficiencies and decreasing the costs of hydrogen prodn. from solar based hydrogen prodn. have a potential to bring them forefront as potential options. The energy and exergy efficiency comparisons indicate the advantages of fossil fuel reforming and biomass gasification over other methods. Overall rankings show that hybrid thermochem. cycles are primarily promising candidates to produce hydrogen in an environmentally benign and cost-effective way. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2MXitVelug%253D%253D&md5= ffd5713d977bf28c318963c8f376a29f 6. 6 Shaner, M. R.; Atwater, H. A.; Lewis, N. S.; McFarland, E. W. A comparative technoeconomic analysis of renewable hydrogen production using solar energy. Energy Environ. Sci. 2016, 9, 2354 - 2371, DOI: 10.1039/C5EE02573G [Crossref], [CAS], Google Scholar 6 A comparative technoeconomic analysis of renewable hydrogen production using solar energy Shaner, Matthew R.; Atwater, Harry A.; Lewis, Nathan S.; McFarland, Eric W. Energy & Environmental Science (2016), 9 (7), 2354-2371CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry) A technoeconomic anal. of photoelectrochem. (PEC) and photovoltaic-electrolytic (PV-E) solar-hydrogen prodn. of 10 000 kg H2 day-1 (3.65 kilotons per yr) was performed to assess the economics of each technol., and to provide a basis for comparison between these technologies as well as within the broader energy landscape. Two PEC systems, differentiated primarily by the extent of solar concn. (unconcd. and 10x concd.) and two PV-E systems, differentiated by the degree of grid connectivity (unconnected and grid supplemented), were analyzed. In each case, a base-case system that used established designs and materials was compared to prospective systems that might be envisioned and developed in the future with the goal of achieving substantially lower overall system costs. With identical overall plant efficiencies of 9.8%, the unconcd. PEC and non-grid connected PV-E system base-case capital expenses for the rated capacity of 3.65 kilotons H2 per yr were $205 MM ($293 per m2 of solar collection area (mS-2), $14.7 WH2,P-1) and $260 MM ($371 mS-2, $18.8 WH2,P-1), resp. The untaxed, plant-gate levelized costs for the hydrogen product (LCH) were $11.4 kg-1 and $12.1 kg-1 for the base-case PEC and PV-E systems, resp. The 10x concd. PEC base-case system capital cost was $160 MM ($428 mS-2, $11.5 WH2,P-1) and for an efficiency of 20% the LCH was $9.2 kg-1. Likewise, the grid supplemented base-case PV-E system capital cost was $66 MM ($441 mS-2, $11.5 WH2,P-1), and with solar-to-hydrogen and grid electrolysis system efficiencies of 9.8% and 61%, resp., the LCH was $6.1 kg-1. As a benchmark, a proton-exchange membrane (PEM) based grid-connected electrolysis system was analyzed. Assuming a system efficiency of 61% and a grid electricity cost of $0.07 kWh-1, the LCH was $5.5 kg-1. A sensitivity anal. indicated that, relative to the base-case, increases in the system efficiency could effect the greatest cost redns. for all systems, due to the areal dependencies of many of the components. The balance-of-systems (BoS) costs were the largest factor in differentiating the PEC and PV-E systems. No single or combination of tech. advancements based on currently demonstrated technol. can provide sufficient cost redns. to allow solar hydrogen to directly compete on a levelized cost basis with hydrogen produced from fossil energy. Specifically, a cost of CO2 greater than ~$800 (ton CO2)-1 was estd. to be necessary for base-case PEC hydrogen to reach price parity with hydrogen derived from steam reforming of methane priced at $12 GJ-1 ($1.39 (kg H2)-1). A comparison with low CO2 and CO2-neutral energy sources indicated that base-case PEC hydrogen is not currently cost-competitive with electrolysis using electricity supplied by nuclear power or from fossil-fuels in conjunction with carbon capture and storage. Solar electricity prodn. and storage using either batteries or PEC hydrogen technologies are currently an order of magnitude greater in cost than electricity prices with no clear advantage to either battery or hydrogen storage as of yet. Significant advances in PEC technol. performance and system cost redns. are necessary to enable cost-effective PEC-derived solar hydrogen for use in scalable grid-storage applications as well as for use as a chem. feedstock precursor to CO2-neutral high energy-d. transportation fuels. Hence such applications are an opportunity for foundational research to contribute to the development of disruptive approaches to solar fuels generation systems that can offer higher performance at much lower cost than is provided by current embodiments of solar fuels generators. Efforts to directly reduce CO2 photoelectrochem. or electrochem. could potentially produce products with higher value than hydrogen, but many, as yet unmet, challenges include catalytic efficiency and selectivity, and CO2 mass transport rates and feedstock cost. Major breakthroughs are required to obtain viable economic costs for solar hydrogen prodn., but the barriers to achieve cost-competitiveness with existing large-scale thermochem. processes for CO2 redn. are even greater. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC28XovFWisb0%253D&md5= 9e19ebf3791f7b67b893bbdeb24ad946 7. 7 Jiang, C.; Moniz, S. J. A.; Wang, A.; Zhang, T.; Tang, J. Photoelectrochemical devices for solar water splitting - materials and challenges. Chem. Soc. Rev. 2017, 46, 4645- 4660, DOI: 10.1039/C6CS00306K [Crossref], [PubMed], [CAS], Google Scholar 7 Photoelectrochemical devices for solar water splitting - materials and challenges Jiang, Chaoran; Moniz, Savio J. A.; Wang, Aiqin; Zhang, Tao; Tang, Junwang Chemical Society Reviews (2017), 46 (15), 4645-4660CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry) A review. It is widely accepted within the community that to achieve a sustainable society with an energy mix primarily based on solar energy we need an efficient strategy to convert and store sunlight into chem. fuels. A photoelectrochem. (PEC) device would therefore play a key role in offering the possibility of carbon-neutral solar fuel prodn. through artificial photosynthesis. The past five years have seen a surge in the development of promising semiconductor materials. In addn., low-cost earth-abundant co-catalysts are ubiquitous in their employment in water splitting cells due to the sluggish kinetics of the oxygen evolution reaction (OER). This review commences with a fundamental understanding of semiconductor properties and charge transfer processes in a PEC device. We then describe various configurations of PEC devices, including single light-absorber cells and multi light-absorber devices (PEC, PV-PEC and PV/electrolyzer tandem cell). Recent progress on both photoelectrode materials (light absorbers) and electrocatalysts is summarized, and important factors which dominate photoelectrode performance, including light absorption, charge sepn. and transport, surface chem. reaction rate and the stability of the photoanode, are discussed. Controlling semiconductor properties is the primary concern in developing materials for solar water splitting. Accordingly, strategies to address the challenges for materials development in this area, such as the adoption of smart architectures, innovative device configuration design, co-catalyst loading, and surface protection layer deposition, are outlined throughout the text, to deliver a highly efficient and stable PEC device for water splitting. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtVGksb3E&md5= 49d52d74c034fa6d8303114f78da958a 8. 8 Nikolaidis, P.; Poullikkas, A. A comparative overview of hydrogen production processes. Renewable Sustainable Energy Rev. 2017, 67, 597- 611, DOI: 10.1016/j.rser.2016.09.044 [Crossref], [CAS], Google Scholar 8 A comparative overview of hydrogen production processes Nikolaidis, Pavlos; Poullikkas, Andreas Renewable & Sustainable Energy Reviews (2017), 67 (), 597-611 CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.) Climate change and fossil fuel depletion are the main reasons leading to hydrogen technol. There are many processes for hydrogen prodn. from both conventional and alternative energy resources such as natural gas, coal, nuclear, biomass, solar and wind. In this work, a comparative overview of the major hydrogen prodn. methods is carried out. The process descriptions along with the tech. and economic aspects of 14 different prodn. methods are discussed. An overall comparison is carried out, and the results regarding both the conventional and renewable methods are presented. The thermochem. pyrolysis and gasification are economically viable approaches providing the highest potential to become competitive on a large scale in the near future while conventional methods retain their dominant role in H2 prodn. with costs in the range of 1.34-2.27 $/kg. Biol. methods appear to be a promising pathway but further research studies are needed to improve their prodn. rates, while the low conversion efficiencies in combination with the high investment costs are the key restrictions for water-splitting technologies to compete with conventional methods. However, further development of these technologies along with significant innovations concerning H2 storage, transportation and utilization, implies the decrease of the national dependence on fossil fuel imports and green hydrogen will dominate over the traditional energy resources. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC28XhsFarurjL&md5= 6cf7ca4fd9c0a23b13ef53d2951ef96c 9. 9 Ball, M.; Weeda, M. The hydrogen economy - Vision or reality?. Int. J. Hydrogen Energy 2015, 40, 7903- 7919, DOI: 10.1016/ j.ijhydene.2015.04.032 [Crossref], [CAS], Google Scholar 9 The hydrogen economy - Vision or reality?1This paper is also published as Chapter 11 'The hydrogen economy - vision or reality?' in Compendium of Hydrogen Energy Volume 4: Hydrogen Use, Safety and the Hydrogen Economy, Edited by Michael Ball, Angelo Basile and T. Nejat Veziroglu, published by Elsevier in 2015, ISBN: 978-1-78242-364-5. For further details see: http:// www.elsevier.com/books/compendium-of-hydrogen-energy/ball/ 978-1-78242-364-5. Ball, Michael; Weeda, Marcel International Journal of Hydrogen Energy (2015), 40 (25), 7903-7919CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.) When looking at future energy systems, hydrogen offers a range of benefits as a clean energy carrier, which are receiving great attention as policy priorities. This is first and foremost as an alternative fuel in the transport sector. Car makers have recently started the market introduction of fuel cell elec. vehicles and are currently entering a pre-com. phase, as they are progressing from prototype vehicles for demonstration to producing small vols. At the same time, market development initiatives aiming at implementing hydrogen refuelling station networks are spreading in Europe, Asia, and the USA. But also in recent years, hydrogen electrolysis has gained considerable attention as a potential flexibility option to help facilitate the large-scale integration of intermittent renewable energies. Given the sustained interest in and controversial discussions on the prospects of hydrogen, this paper aims to provide a comprehensive coverage of the most relevant aspects related to the wider use of hydrogen in the energy system, including the most recent developments and insights. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2MXntFKhs78%253D&md5= 9e90e48a27f79d9b4a7a4e1a761fe4f1 10. 10 Dutta, S. A review on production, storage of hydrogen and its utilization as an energy resource. J. Ind. Eng. Chem. 2014, 20, 1148- 1156, DOI: 10.1016/j.jiec.2013.07.037 [Crossref], [CAS], Google Scholar 10 A review on production, storage of hydrogen and its utilization as an energy resource Dutta, Suman Journal of Industrial and Engineering Chemistry (Amsterdam, Netherlands) (2014), 20 (4), 1148-1156CODEN: JIECFI; ISSN: 1226-086X. (Elsevier B.V.) A review. Energy price is rising due to rapid depletion of fossil fuels. Development of renewable and non-polluting energy resources is necessary for reducing pollution level caused by those conventional fuels. Researchers have recognized hydrogen (H2) as such an energy source. Hydrogen is a potential non-carbon based energy resource, which can replace fossil fuels. Hydrogen is considered as the alternative fuel as it could be generated from clean and green sources. Despite many advantages, storage of hydrogen is a serious problem. Due to high inflammability, adequate safety measures should be taken during the prodn., storage, and use of H2 fuel. This review article elucidates prodn. methods and storage of hydrogen. Besides this safety related to H2 handling in refilling station, and automobiles has also been discussed. Study shows that safety program and awareness could be fruitful for increasing the acceptance of hydrogen as fuel. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtlansrjI&md5= 8b26df1b96cc96f7803331d1957f1dba 11. 11 McCrory, C. C. Benchmarking hydrogen evolving reaction and oxygen evolving reaction electrocatalysts for solar water splitting devices. J. Am. Chem. Soc. 2015, 137, 4347- 4357, DOI: 10.1021/ ja510442p [ACS Full Text ACS Full Text], [CAS], Google Scholar 11 Benchmarking Hydrogen Evolving Reaction and Oxygen Evolving Reaction Electrocatalysts for Solar Water Splitting Devices McCrory, Charles C. L.; Jung, Suho; Ferrer, Ivonne M.; Chatman, Shawn M.; Peters, Jonas C.; Jaramillo, Thomas F. Journal of the American Chemical Society (2015), 137 (13), 4347-4357CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society) Objective comparisons of electrocatalyst activity and stability using std. methods under identical conditions are necessary to evaluate the viability of existing electrocatalysts for integration into solar-fuel devices as well as to help inform the development of new catalytic systems. Herein, the authors use a std. protocol as a primary screen for evaluating the activity, short-term (2 h) stability, and electrochem. active surface area (ECSA) of 18 electrocatalysts for the H evolution reaction (HER) and 26 electrocatalysts for the O evolution reaction (OER) under conditions relevant to an integrated solar H2O-splitting device in aq. acidic or alk. soln. The primary figure of merit is the overpotential necessary to achieve a magnitude c.d. of 10 mA cm-2 per geometric area, the approx. c.d. expected for a 10% efficient solar-to-fuels conversion device under 1 sun illumination. The specific activity per ECSA of each material is also reported. Among HER catalysts, several could operate at 10 mA cm-2 with overpotentials <0.1 V in acidic and/or alk. solns. Among OER catalysts in acidic soln., no nonnoble metal based materials showed promising activity and stability, whereas in alk. soln. many OER catalysts performed with similar activity achieving 10 mA cm-2 current densities at overpotentials of ~0.33-0.5 V. Most OER catalysts showed comparable or better specific activity per ECSA when compared to Ir and Ru catalysts in alk. solns., while most HER catalysts showed much lower specific activity than Pt in both acidic and alk. solns. For select catalysts, addnl. secondary screening measurements were conducted including faradaic efficiency and extended stability measurements. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2MXisFyqtrw%253D&md5= 7a45e7400dde5988037aab80ed076b75 12. 12 Kwong, W. L. Cationic Vacancy Defects in Iron Phosphide: A Promising Route toward Efficient and Stable Hydrogen Evolution by Electrochemical Water Splitting. ChemSusChem 2017, 10, 4544- 4551 , DOI: 10.1002/cssc.201701565 [Crossref], [PubMed], [CAS], Google Scholar 12 Cationic Vacancy Defects in Iron Phosphide: A Promising Route toward Efficient and Stable Hydrogen Evolution by Electrochemical Water Splitting Kwong, Wai Ling; Gracia-Espino, Eduardo; Lee, Cheng Choo; Sandstroem, Robin; Wagberg, Thomas; Messinger, Johannes ChemSusChem (2017), 10 (22), 4544-4551CODEN: CHEMIZ; ISSN: 1864-5631. (Wiley-VCH Verlag GmbH & Co. KGaA) Engineering the electronic properties of transition metal phosphides has shown great effectiveness in improving their intrinsic catalytic activity for the hydrogen evolution reaction (HER) in water splitting applications. Herein, the creation of Fe vacancies is reported for the first time as an approach to modulate the electronic structure of iron phosphide (FeP). The Fe-vacancies were produced by chem. leaching of Mg that was introduced into FeP as sacrificial dopant. The obtained Fe vacancy-rich FeP nanoparticulate films, which were deposited on Ti foil, show excellent HER activity compared to pristine FeP and Mg-doped FeP, achieving a c.d. of 10 mA cm-2 at overpotentials of 108 mV in 1 M KOH and 65 mV in 0.5 M H2SO4, with a near-100 % Faradaic efficiency. The theor. and exptl. analyses reveal that the improved HER activity originates from the presence of Fe vacancies, which lead to a synergistic modulation of the structural and electronic properties that result in a near-optimal hydrogen adsorption free energy and enhanced proton trapping. The success in catalytic improvement through the introduction of cationic vacancy defects has not only demonstrated the potential of Fe-vacancy-rich FeP as highly efficient, earth abundant HER catalyst, but also opens up an exciting pathway for activating other promising catalysts for electrochem. water splitting. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2sXhslentb%252FM&md5= 5d639d54efddbe243a2404c41e16b49e 13. 13 Zhang, C.; Shi, Y.; Yu, Y.; Du, Y.; Zhang, B. Engineering Sulfur Defects, Atomic Thickness, and Porous Structures into Cobalt Sulfide Nanosheets for Efficient Electrocatalytic Alkaline Hydrogen Evolution. ACS Catal. 2018, 8, 8077- 8083, DOI: 10.1021 /acscatal.8b02056 [ACS Full Text ACS Full Text], [CAS], Google Scholar 13 Engineering Sulfur Defects, Atomic Thickness, and Porous Structures into Cobalt Sulfide Nanosheets for Efficient Electrocatalytic Alkaline Hydrogen Evolution Zhang, Chao; Shi, Yanmei; Yu, Yifu; Du, Yonghua; Zhang, Bin ACS Catalysis (2018), 8 (9), 8077-8083CODEN: ACCACS; ISSN: 2155-5435. (American Chemical Society) The development of nonprecious metal-based electrocatalysts with high mass activity and efficient atom utilization for alkali hydrogen evolution reaction (HER) is of great importance for the prepn. of hydrogen resource. The combination of ultrathin and porous structure, esp. with the assistance of vacancy, is expected to be beneficial for achievement of high mass activity, but the development of a facile, robust, and generalized strategy to engineer ultrathin, porous, and vacancy-rich structure into nonlayer structured transition metal-based electrocatalysts is highly challenging. Here, a plasma-induced dry exfoliation method is proposed to prep. nonlayer structured Co3S4 ultrathin porous nanosheets with abundant sulfur vacancies (Co3S4 PNSvac), which show an onset overpotential of only 18 mV and an extremely large mass activity of 1056.6 A g-1 at an overpotential of 200 mV. Exptl. results and theor. calcns. confirm that the efficient alk. HER performance could be attributed to the abundant active sites, good intrinsic activity, and accelerated electron/mass transfer. Addnl., the plasma-assisted conversion method can also be extended to fabricate CoSe2 and NiSe2 ultrathin porous nanosheets with selenium vacancies. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC1cXhsVWrsLfE&md5= 81bab2e06a434035c69d2fc366e8c450 14. 14 Zhang, T. Engineering oxygen vacancy on NiO nanorod arrays for alkaline hydrogen evolution. Nano Energy 2018, 43, 103- 109, DOI: 10.1016/j.nanoen.2017.11.015 [Crossref], [CAS], Google Scholar 14 Engineering oxygen vacancy on NiO nanorod arrays for alkaline hydrogen evolution Zhang, Tong; Wu, Meng-Ying; Yan, Dong-Yang; Mao, Jing; Liu, Hui; Hu, Wen-Bin; Du, Xi-Wen; Ling, Tao; Qiao, Shi-Zhang Nano Energy (2018), 43 (), 103-109CODEN: NEANCA; ISSN:2211-2855. (Elsevier Ltd.) Development of low-cost electrocatalysts toward oxygen evolution (OER) and hydrogen evolution reactions (HER) is crucial for large-scale and clean hydrogen prodn. Cost-effective transition metal oxide-based catalysts are superbly active for OER; however, their applications in catalyzing HER remain challenging due to unsatisfactory activity and intrinsically poor electronic cond. Here, we report the synthesis of NiO nanorods (NRs) with abundant oxygen (O) vacancies via a facile cation exchange strategy. Based on the exptl. studies and d. functional theory calcns., we demonstrate that the chem. and electronic property of NiO NRs is successfully optimized through O-vacancy engineering; the O-vacancies on the surface of NiO NRs remarkably enhance their electronic conduction and promote HER reaction kinetics simultaneously. The resulting NiO NRs exhibit excellent alk. HER catalytic activity and durability. Furthermore, these specific designed NiO NRs in situ on carbon fiber paper substrates were directly employed as both HER and OER catalysts for overall water splitting, affording better performance than benchmark Pt and RuO2 catalysts. The successful synthesis of these metal oxides nanomaterials with abundant O-vacancies may pave a new path for rationally fabricating efficient HER/OER bi-functional catalysts. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvVWms7zP&md5= 1f8d02f072ce1920bd117a47a0961a99 15. 15 Zhao, Y. Defect-Engineered Ultrathin d-MnO2Nanosheet Arrays as Bifunctional Electrodes for Efficient Overall Water Splitting. Adv. Energy Mater. 2017, 7, 1700005, DOI: 10.1002/aenm.201700005 [Crossref], Google Scholar There is no corresponding record for this reference. 16. 16 Du, H.; Kong, R. M.; Guo, X.; Qu, F.; Li, J. Recent progress in transition metal phosphides with enhanced electrocatalysis for hydrogen evolution. Nanoscale 2018, 10, 21617- 21624, DOI: 10.1039/C8NR07891B [Crossref], [PubMed], [CAS], Google Scholar 16 Recent progress in transition metal phosphides with enhanced electrocatalysis for hydrogen evolution Du, Huitong; Kong, Rong-Mei; Guo, Xiaoxi; Qu, Fengli; Li, Jinghong Nanoscale (2018), 10 (46), 21617-21624CODEN: NANOHL; ISSN: 2040-3372. (Royal Society of Chemistry) Increasing demand for hydrogen energy has boosted the exploration of inexpensive and effective catalysts. Transition metal phosphides (TMPs) have been proven as excellent catalysts for the hydrogen evolution reaction (HER). Very recently, the search for TMP-based catalysts has being mainly directed at enhanced electrocatalytic performance. Hence, a concluded guideline for enhancing HER activity is highly desired. In this mini review, we briefly summarize the most recent and instructive developments in the design of TMP-based catalysts with enhanced electrocatalysis for hydrogen evolution from compn. and structure engineering strategies. These strategies and perspectives are also meaningful for designing other inexpensive and high-performance catalysts. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC1cXitVaqurjK&md5= e4a377dd0d57fb7b989383498694ecb0 17. 17 McKone, J. R.; Sadtler, B. F.; Werlang, C. A.; Lewis, N. S.; Gray, H. B. Ni-Mo Nanopowders for Efficient Electrochemical Hydrogen Evolution. ACS Catal. 2013, 3, 166- 169, DOI: 10.1021/ cs300691m [ACS Full Text ACS Full Text], [CAS], Google Scholar 17 Ni-Mo Nanopowders for Efficient Electrochemical Hydrogen Evolution McKone, James R.; Sadtler, Bryce F.; Werlang, Caroline A.; Lewis, Nathan S.; Gray, Harry B. ACS Catalysis (2013), 3 (2), 166-169CODEN: ACCACS; ISSN:2155-5435 . (American Chemical Society) Earth-abundant metals are attractive alternatives to the noble metal composite catalysts that are used in water electrolyzers based on proton-exchange membrane technol. Ni-Mo alloys were previously developed for the hydrogen evolution reaction (HER), but synthesis methods to date were limited to formation of catalyst coatings directly on a substrate. A method is reported for generating unsupported nanopowders of Ni-Mo, which can be suspended in common solvents and cast onto arbitrary substrates. The mass-specific catalytic activity under alk. conditions approaches that of the most active reported non-noble HER catalysts, and the coatings display good stability under alk. conditions. Turnover frequencies are also estd. per surface atom at various overpotentials and concluded that the activity enhancement for Ni-Mo relative to pure Ni is due to a combination of increased surface area and increased fundamental catalytic activity. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC38XhslOls77L&md5= 8b191b25429211814582ee2dddec630d 18. 18 Zeng, M.; Li, Y. Recent advances in heterogeneous electrocatalysts for the hydrogen evolution reaction. J. Mater. Chem. A 2015, 3, 14942- 14962, DOI: 10.1039/C5TA02974K [Crossref], [CAS], Google Scholar 18 Recent advances in heterogeneous electrocatalysts for the hydrogen evolution reaction Zeng, Min; Li, Yanguang Journal of Materials Chemistry A: Materials for Energy and Sustainability (2015), 3 (29), 14942-14962CODEN: JMCAET; ISSN: 2050-7496. (Royal Society of Chemistry) The hydrogen evolution reaction plays a decisive role in a range of electrochem. and photoelectrochem. devices. It requires efficient and robust electrocatalysts to lower the reaction overpotential and minimize energy consumption. Over the last decade, we have witnessed a rapid rise in new electrocatalysts, particularly those based on non-precious metals. Some of them approach the activity of precious metal benchmarks. Here, we present a comprehensive overview of the recent developments of heterogeneous electrocatalysts for the hydrogen evolution reaction. Detailed discussion is organized from precious metals to non-precious metal compds. including alloys, chalcogenides, carbides, nitrides, borides and phosphides, and finally to metal-free materials. Emphasis is placed on the challenges facing these electrocatalysts and solns. for further improving their performance. We conclude with a perspective on the development of future HER electrocatalysts. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2MXpt1Ogsr0%253D&md5= b3ff2533400b5ecf569482777bc88c6d 19. 19 Vij, V. Nickel-Based Electrocatalysts for Energy-Related Applications: Oxygen Reduction, Oxygen Evolution, and Hydrogen Evolution Reactions. ACS Catal. 2017, 7, 7196- 7225, DOI: 10.1021/acscatal.7b01800 [ACS Full Text ACS Full Text], [CAS], Google Scholar 19 Nickel-Based Electrocatalysts for Energy-Related Applications: Oxygen Reduction, Oxygen Evolution, and Hydrogen Evolution Reactions Vij, Varun; Sultan, Siraj; Harzandi, Ahmad M.; Meena, Abhishek; Tiwari, Jitendra N.; Lee, Wang-Geun; Yoon, Taeseung; Kim, Kwang S. ACS Catalysis (2017), 7 (10), 7196-7225CODEN: ACCACS; ISSN: 2155-5435. (American Chemical Society) A review. The persistently increasing energy consumption and the low abundance of conventional fuels have raised serious concerns all over the world. Thus, the development of technol. for clean-energy prodn. has become the major research priority worldwide. The globalization of advanced energy conversion technologies like rechargeable metal-air batteries, regenerated fuel cells, and H2O-splitting devices was greatly benefitted by the development of apposite catalytic materials that can proficiently carry out the pertinent electrochem. processes like O redn. reaction (ORR), O evolution reaction (OER), H evolution reaction (HER), and H2O hydrolysis. Despite a handful of superbly performing com. catalysts, the high cost and low electrochem. stability of precursors have consistently discouraged their long-term viability. As a promising substitute of conventional Pt-, Pd-, Ir-, Au-, Ag-, and Ru-based catalysts, various transition-metal (TM) ions (for example, Fe, Co, Mo, Ni, V, Cu, etc.) have been exploited to develop advanced electroactive materials to outperform the state-of-the-art catalytic properties. Among these TMs, Ni has emerged as one of the most hopeful constituents due to its exciting electronic properties and anticipated synergistic effect to dramatically alter surface properties of materials to favor electrocatalysis. This review article will broadly confer about recent reports on Ni-based nanoarchitectured materials and their applications toward ORR, OER, HER, and whole H2O splitting. From these applications and properties of Ni derivs., a futuristic outlook of these materials also was presented. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsVeksb7N&md5= c5965edea15dec39a52344e670d6b213 20. 20 Sharifi, T. Hierarchical self-assembled structures based on nitrogen-doped carbon nanotubes as advanced negative electrodes for Li-ion batteries and 3D microbatteries. J. Power Sources 2015 , 279, 581- 592, DOI: 10.1016/j.jpowsour.2015.01.036 [Crossref], [CAS], Google Scholar 20 Hierarchical self-assembled structures based on nitrogen-doped carbon nanotubes as advanced negative electrodes for Li-ion batteries and 3D microbatteries Sharifi, Tiva; Valvo, Mario; Gracia-Espino, Eduardo; Sandstroem, Robin; Edstroem, Kristina; Waagberg, Thomas Journal of Power Sources (2015), 279 (), 581-592CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.) Hierarchical structures based on C paper and multi-walled N-doped C nanotubes were fabricated and subsequently decorated with hematite nanorods to obtain advanced 3-dimensional architectures for Li-ion battery neg. electrodes. The C paper provides a versatile metal-free 3-dimensional current collector ensuring a good elec. contact of the active materials to its C fiber network. Firstly, the N-doped C nanotubes onto the C paper were studied and a high footprint area capacity of 2.1 mA h cm-2 at 0.1 mA cm-2 was obtained. The Li can be stored in the inter-wall regions of the nanotubes, mediated by the defects formed on their walls by the N atoms. Secondly, the incorporation of hematite nanorods raised the footprint area capacity to 2.25 mA h cm-2 at 0.1 mA cm-2. However, the repeated conversion/de-conversion of Fe2O3 limited both coulombic and energy efficiencies for these electrodes, which did not perform as well as those including only the N-doped C nanotubes at higher current densities. Thirdly, long-cycling tests showed the robust Li insertion mechanism in these N-doped carbonaceous structures, which yielded an unmatched footprint area capacity enhancement up to 1.95 mA h cm-2 after 60 cycles at 0.3 mA cm-2 and an overall capacity of 204 mA h g-1 referred to the mass of the entire electrode. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2MXksl2ntA%253D%253D&md5= d6a91dc9ceb9827fa7a350729c288b1b 21. 21 Ekspong, J. Stabilizing Active Edge Sites in Semicrystalline Molybdenum Sulfide by Anchorage on Nitrogen-Doped Carbon Nanotubes for Hydrogen Evolution Reaction. Adv. Funct. Mater. 2016, 26, 6766- 6776, DOI: 10.1002/adfm.201601994 [Crossref], [CAS], Google Scholar 21 Stabilizing Active Edge Sites in Semicrystalline Molybdenum Sulfide by Anchorage on Nitrogen-Doped Carbon Nanotubes for Hydrogen Evolution Reaction Ekspong, Joakim; Sharifi, Tiva; Shchukarev, Andrey; Klechikov, Alexey; Wagberg, Thomas; Gracia-Espino, Eduardo Advanced Functional Materials (2016), 26 (37), 6766-6776CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA) Finding an abundant and cost-effective electrocatalyst for the hydrogen evolution reaction (HER) is crucial for a global prodn. of hydrogen from water electrolysis. This work reports an exceptionally large surface area hybrid catalyst electrode comprising semicryst. molybdenum sulfide (MoS2+x) catalyst attached on a substrate based on nitrogen-doped carbon nanotubes (N-CNTs), which are directly grown on carbon fiber paper (CP). It is shown here that nitrogen-doping of the carbon nanotubes improves the anchoring of MoS2+x catalyst compared to undoped carbon nanotubes and concurrently stabilizes a semicryst. structure of MoS2+x with a high exposure of active sites for HER. The well-connected constituents of the hybrid catalyst are shown to facilitate electron transport and as a result of the good attributes, the MoS2+x/N-CNT/CP electrode exhibits an onset potential of -135 mV for HER in 0.5 M H2SO4, a Tafel slope of 36 mV dec-1, and high stability at a c.d. of -10 mA cm-2. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC28Xht1Wmt77J&md5= 4e3c0c0578df64b39a737a2c8f21ecec 22. 22 Zamudio, A. Efficient Anchoring of Silver Nanoparticles on N-Doped Carbon Nanotubes. Small 2006, 2, 346- 350, DOI: 10.1002/ smll.200500348 [Crossref], [PubMed], [CAS], Google Scholar 22 Efficient anchoring of silver nanoparticles on N-doped carbon nanotubes Zamudio, Adalberto; Elias, Ana L.; Rodriguez-Manzo, Julio A.; Lopez-Urias, Florentino; Rodriguez-Gattorno, Geonel; Lupo, Fabio; Ruhle, Manfred; Smith, David J.; Terrones, Humberto; Diaz, David; Terrones, Mauricio Small (2006), 2 (3), 346-350CODEN: SMALBC; ISSN:1613-6810. ( Wiley-VCH Verlag GmbH & Co. KGaA) Getting on the tube: A single-step method to attach silver nanoparticles on the surfaces of nitrogen-doped multi-walled carbon nanotubes is described (as depicted in the picture). Ag nanoparticles (2-10 nm diam.) are synthesized by redn. of a Ag salt, and then mixed with the nanotubes in a technique that does not require acid treatment. Similar methods with undoped nanotubes yield less well-coated nanotubes. Interactions with solvent species are believed to play a role in the decoration mechanism. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BD28Xhs1aqs7g%253D&md5= be7d392adc2619d6b70d32d20a36ca42 23. 23 Wang, W.; Luo, J.; Chen, S. Carbon oxidation reactions could misguide the evaluation of carbon black-based oxygen-evolution electrocatalysts. Chem. Commun. (Cambridge, U. K.) 2017, 53, 11556- 11559, DOI: 10.1039/C7CC04611A [Crossref], [PubMed], [CAS], Google Scholar 23 Carbon oxidation reactions could misguide the evaluation of carbon black-based oxygen-evolution electrocatalysts Wang, Wang; Luo, Jin; Chen, Shengli Chemical Communications (Cambridge, United Kingdom) (2017), 53 ( 84), 11556-11559CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry) A variety of carbon-based materials have been reported as electrocatalysts towards the O evolution reaction. However, C oxidn. during the OER was rarely considered or even neglected in most of the reports. Here, using C black as a model material, we develop a method to est. the contribution of C oxidn. reactions (CORs) to the measured current during the OER test. It is shown that the CORs could result in significant overestimation of the OER activity of C black-based electrocatalysts. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsFylsb3P&md5= 91905a983f384c71096aa9c9b191f11b 24. 24 Lu, X.; Yim, W. L.; Suryanto, B. H.; Zhao, C. Electrocatalytic oxygen evolution at surface-oxidized multiwall carbon nanotubes. J. Am. Chem. Soc. 2015, 137, 2901- 2907, DOI: 10.1021/ja509879r [ACS Full Text ACS Full Text], [CAS], Google Scholar 24 Electrocatalytic Oxygen Evolution at Surface-Oxidized Multiwall Carbon Nanotubes Lu, Xunyu; Yim, Wai-Leung; Suryanto, Bryan H. R.; Zhao, Chuan Journal of the American Chemical Society (2015), 137 (8), 2901-2907CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society) Large-scale storage of renewable energy in the form of hydrogen (H2) fuel via electrolytic water splitting requires the development of water oxidn. catalysts that are efficient and abundant. Carbon-based nanomaterials such as carbon nanotubes have attracted significant applications for use as substrates for anchoring metal-based nanoparticles. It is shown that, upon mild surface oxidn., hydrothermal annealing and electrochem. activation, multiwall carbon nanotubes (MWCNTs) themselves are effective water oxidn. catalysts, which can initiate the oxygen evolution reaction (OER) at overpotentials of 0.3 V in alk. media. Oxygen-contg. functional groups such as ketonic C=O generated on the outer wall of MWCNTs are found to play crucial roles in catalyzing OER by altering the electronic structures of the adjacent carbon atoms and facilitates the adsorption of OER intermediates. The well-preserved microscopic structures and highly conductive inner walls of MWCNTs enable efficient transport of the electrons generated during OER. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2MXitlWmsL4%253D&md5= e9e1a4bc60ad7bbf7e8b3412516b0d70 25. 25 Gong, M. An advanced Ni-Fe layered double hydroxide electrocatalyst for water oxidation. J. Am. Chem. Soc. 2013, 135, 8452- 8455, DOI: 10.1021/ja4027715 [ACS Full Text ACS Full Text], [CAS], Google Scholar 25 An Advanced Ni-Fe Layered Double Hydroxide Electrocatalyst for Water Oxidation Gong, Ming; Li, Yanguang; Wang, Hailiang; Liang, Yongye; Wu, Justin Z.; Zhou, Jigang; Wang, Jian; Regier, Tom; Wei, Fei; Dai, Hongjie Journal of the American Chemical Society (2013), 135 (23), 8452-8455CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society) Highly active, durable, and cost-effective electrocatalysts for H2O oxidn. to evolve O gas hold a key to a range of renewable energy solns., including H2O-splitting and rechargeable metal-air batteries. Here, the authors report the synthesis of ultrathin Ni-Fe layered double hydroxide (NiFe-LDH) nanoplates on mildly oxidized multi-walled C nanotubes (CNTs). Incorporation of Fe into the Ni hydroxide induced the formation of NiFe-LDH. The cryst. NiFe-LDH phase in nanoplate form is highly active for O evolution reaction in alk. solns. For NiFe-LDH grown on a network of CNTs, the resulting NiFe-LDH/CNT complex exhibits higher electrocatalytic activity and stability for O evolution than com. precious metal Ir catalysts. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC3sXot1alu78%253D&md5= 90ff0f80019554e2e5d436a5590f7cf7 26. 26 Song, F.; Hu, X. Exfoliation of layered double hydroxides for enhanced oxygen evolution catalysis. Nat. Commun. 2014, 5, 4477, DOI: 10.1038/ncomms5477 [Crossref], [PubMed], [CAS], Google Scholar 26 Exfoliation of layered double hydroxides for enhanced oxygen evolution catalysis Song, Fang; Hu, Xile Nature Communications (2014), 5 (), 4477CODEN: NCAOBW; ISSN: 2041-1723. (Nature Publishing Group) The oxygen evolution reaction is a key reaction in water splitting. The common approach in the development of oxygen evolution catalysts is to search for catalytic materials with new and optimized chem. compns. and structures. Here we report an orthogonal approach to improve the activity of catalysts without alternating their compns. or structures. Specifically, liq. phase exfoliation is applied to enhance the oxygen evolution activity of layered double hydroxides. The exfoliated single-layer nanosheets exhibit significantly higher oxygen evolution activity than the corresponding bulk layered double hydroxides in alk. conditions. The nanosheets from nickel iron and nickel cobalt layered double hydroxides outperform a com. iridium dioxide catalyst in both activity and stability. The exfoliation creates more active sites and improves the electronic cond. This work demonstrates the promising catalytic activity of single-layered double hydroxides for the oxygen evolution reaction. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2cXitVShs7%252FE&md5= ca5d2d80f1409c80b596494e74520a10 27. 27 Liu, L.; Wu, H.; She, L. Tuning Microstructures of Iron-Nickel Alloy Catalysts for Efficient Oxygen Evolution Reaction. Chem. J. Chin. Univ. 2020, 41, 1083- 1090, DOI: 10.7503/cjcu20190660 [Crossref], Google Scholar There is no corresponding record for this reference. 28. 28 Zhang, B. Homogeneously dispersed, multimetal oxygen-evolving catalysts. Science 2016, 352, 333- 337, DOI: 10.1126/ science.aaf1525 [Crossref], [PubMed], [CAS], Google Scholar 28 Homogeneously dispersed multimetal oxygen-evolving catalysts Zhang, Bo; Zheng, Xueli; Voznyy, Oleksandr; Comin, Riccardo; Bajdich, Michal; Garcia-Melchor, Max; Han, Lili; Xu, Jixian; Liu, Min; Zheng, Lirong; Garcia de Arquer, F. Pelayo; Dinh, Cao Thang; Fan, Fengjia; Yuan, Mingjian; Yassitepe, Emre; Chen, Ning; Regier, Tom; Liu, Pengfei; Li, Yuhang; De Luna, Phil; Janmohamed, Alyf; Xin, Huolin L.; Yang, Huagui; Vojvodic, Aleksandra; Sargent, Edward H. Science (Washington, DC, United States) (2016), 352 (6283), 333-337CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science) Earth-abundant first-row (3d) transition metal-based catalysts were developed for the oxygen-evolution reaction (OER); however, they operate at overpotentials substantially above thermodn. requirements. D. functional theory suggested that non-3d high-valency metals such as tungsten can modulate 3d metal oxides, providing near-optimal adsorption energies for OER intermediates. A room-temp. synthesis is developed to produce gelled oxyhydroxides materials with an atomically homogeneous metal distribution. These gelled FeCoW oxyhydroxides exhibit the lowest overpotential (191 mV) reported at 10 mA per square centimeter in alk. electrolyte. The catalyst shows no evidence of degrdn. after more than 500 h of operation. X-ray absorption and computational studies reveal a synergistic interplay between tungsten, iron, and cobalt in producing a favorable local coordination environment and electronic structure that enhance the energetics for OER. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC28Xlsl2isLk%253D&md5= d2b80a4091e08859b95ca5900015c186 29. 29 Jin, Y. Porous MoO2 Nanosheets as Non-noble Bifunctional Electrocatalysts for Overall Water Splitting. Adv. Mater. 2016, 28, 3785- 3790, DOI: 10.1002/adma.201506314 [Crossref], [PubMed], [CAS], Google Scholar 29 Porous MoO2 Nanosheets as Non-noble Bifunctional Electrocatalysts for Overall Water Splitting Jin, Yanshuo; Wang, Haotian; Li, Junjie; Yue, Xin; Han, Yujie; Shen, Pei Kang; Cui, Yi Advanced Materials (Weinheim, Germany) (2016), 28 (19), 3785-3790 CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA) Porous MoO2 nanosheets were directly grown on com. nickel foam without binder by a simple wet-chem. route first and then with an annealing treatment. The porous MoO2 shows much higher activity toward both HER and OER than the compact MoO2, which could be attributed to the higher surface area and more active sites contributed by porous nanostructuring. As an active and stable bifunctional electrocatalyst for overall water splitting, the porous MoO2 needs a cell voltage of only about 1.53 V to achieve c.d. of 10 mA cm-2 and maintains its activity for at least 24 h in a two-electrode configuration and 1 M KOH. The water-splitting device can be powered by an AA battery with a nominal voltage of 1.5 V at room temp. Porous MoO2 is one of the best high-performance bifunctional electrocatalysts for overall water splitting and this work offers an attractive cost-effective catalytic material toward overall water splitting. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC28Xks1ekur8%253D&md5= 7fa8404fd632e9db05e4b2411c02924a 30. 30 Krstajic, N. V. Non-noble metal composite cathodes for hydrogen evolution. Part I: The Ni-MoOx coatings electrodeposited from Watt's type bath containing MoO3 powder particles. Int. J. Hydrogen Energy 2011, 36, 6441- 6449, DOI: 10.1016/ j.ijhydene.2011.02.105 [Crossref], [CAS], Google Scholar 30 Non-noble metal composite cathodes for hydrogen evolution. The Ni-MoOx coatings electrodeposited from Watt's type bath containing MoO3 powder particles Krstajic, N. V.; Gajic-Krstajic, Lj.; Lacnjevac, U.; Jovic, B. M.; Mora, S.; Jovic, V. D. International Journal of Hydrogen Energy (2011), 36 (11), 6441-6449CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.) In this work, the Ni-MoOx coatings have been prepd. and characterized in view of their possible application as electrocatalysts for hydrogen evolution reaction (HER) in alk. soln. The procedure of deposition of Ni-MoOx coatings from the Watt's type bath contg. MoO3 powder particles onto Ni mesh, under the conditions of simulated industrial deposition conditions for com. cathodes, has been presented. The morphol. of the obtained coatings was investigated by SEM, the compn. by EDS and the phase compn. by XRD techniques. The polarization characteristics for hydrogen evolution on the obtained Ni-MoOx coatings were investigated in the 32 wt. % NaOH at 90 degC and compared with the one recorded for the com. De Nora's coating (DN). It was shown that the best Ni-MoOx coating exhibits almost identical polarization characteristics as the com. one. By the cross section and XRD anal. of deposited samples it was confirmed that MoO3 powder particles were not occluded by the Ni deposit and that molybdenum species were deposited from the molybdate ions formed by dissoln. of MoO3, following the mechanism of induced co-deposition. The reaction mechanism for MoO3 phase deposition has also been proposed. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC3MXlslKrsrw%253D&md5= fd7513b6a7dd6ef5daee4e08f885a5c8 31. 31 Luo, Z. Mesoporous MoO3-x Material as an Efficient Electrocatalyst for Hydrogen Evolution Reactions. Adv. Energy Mater. 2016, 6, 1600528, DOI: 10.1002/aenm.201600528 [Crossref], Google Scholar There is no corresponding record for this reference. 32. 32 Jin, Y.; Shen, P. K. Nanoflower-like metallic conductive MoO2 as a high-performance non-precious metal electrocatalyst for the hydrogen evolution reaction. J. Mater. Chem. A 2015, 3, 20080- 20085, DOI: 10.1039/C5TA06018D [Crossref], [CAS], Google Scholar 32 Nanoflower-like metallic conductive MoO2 as a high-performance non-precious metal electrocatalyst for the hydrogen evolution reaction Jin, Yanshuo; Shen, Pei Kang Journal of Materials Chemistry A: Materials for Energy and Sustainability (2015), 3 (40), 20080-20085CODEN: JMCAET; ISSN: 2050-7496. (Royal Society of Chemistry) Searching for nonprecious metal electrocatalysts with high activity and stability for the H evolution reaction (HER) has attracted considerable attention. Herein, the authors report the synthesis of nanoflower-like MoO2 on Ni foam (NFL MoO2/NF). Remarkably, as a HER electrocatalyst operating in alk. electrolytes, NFL MoO2/NF exhibits high stability and activity. The onset potential of NFL MoO2/NF is almost 0 V vs. the reversible H electrode (RHE) and bubbles can be produced on the surface of NFL MoO2/NF under a static overpotential of only 10 mV, comparable to com. Pt/C. NFL MoO2/NF needs overpotentials of only ~55 and 80 mV to achieve current densities of 10 and 20 mA cm-2, resp. NFL MoO2/NF has superior stability in the long-term electrochem. process and retains 94.3% of its initial c.d. after 25 h. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsVygtrfK&md5= 9c0990cce798fdbba474082fa16437a2 33. 33 Tian, J. Self-supported NiMo hollow nanorod array: an efficient 3D bifunctional catalytic electrode for overall water splitting. J. Mater. Chem. A 2015, 3, 20056- 20059, DOI: 10.1039/C5TA04723D [Crossref], [CAS], Google Scholar 33 Self-supported NiMo hollow nanorod array: an efficient 3D bifunctional catalytic electrode for overall water splitting Tian, Jingqi; Cheng, Ningyan; Liu, Qian; Sun, Xuping; He, Yuquan; Asiri, Abdullah M. Journal of Materials Chemistry A: Materials for Energy and Sustainability (2015), 3 (40), 20056-20059CODEN: JMCAET; ISSN: 2050-7496. (Royal Society of Chemistry) Large-scale industrial application of electrochem. H2O splitting calls for remarkable nonnoble metal electrocatalysts. Herein, the authors report on the synthesis of a NiMo-alloy hollow nanorod array supported on Ti mesh (NiMo HNRs/TiM) using a template-assisted electrodeposition method. The NiMo HNRs/TiM behaves as a durable efficient O evolution anode with 10 mA cm-2 at an overpotential of 310 mV in 1.0 M KOH. Coupled with its superior catalytic performance for H evolution with 10 mA cm-2 at an overpotential of 92 mV, the authors made an alk. electrolyzer using this bifunctional electrode with 10 mA cm-2 at a cell voltage of 1.64 V. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsVSjurzN&md5= aa961cfc94d2497ece482e6a934cef5e 34. 34 Wiggins-Camacho, J. D.; Stevenson, K. J. Effect of Nitrogen Concentration on Capacitance, Density of States, Electronic Conductivity, and Morphology of N-Doped Carbon Nanotube Electrodes. J. Phys. Chem. C 2009, 113, 19082- 19090, DOI: 10.1021/jp907160v [ACS Full Text ACS Full Text], [CAS], Google Scholar 34 Effect of Nitrogen Concentration on Capacitance, Density of States, Electronic Conductivity, and Morphology of N-Doped Carbon Nanotube Electrodes Wiggins-Camacho, Jaclyn D.; Stevenson, Keith J. Journal of Physical Chemistry C (2009), 113 (44), 19082-19090 CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society) Heteroatom doping (e.g., boron and nitrogen) of graphitic carbon lattices affects various physicochem. properties of sp2 carbon materials. The influence of nitrogen doping in carbon nanotubes (N-CNTs) on their electrochem. and elec. properties such as the differential capacitance, d. of states at the Fermi level (D (EF)), bulk cond., and work function is presented. Studies were performed on free-standing N-CNTs electrode mats to understand the intrinsic physicochem. properties of the material without relying on the secondary influence of another conductive support. N-Doping levels ranging from 0 to 7.4 at.% N were examd., and electrochem. impedance spectroscopy (EIS) was used to evaluate the differential capacitance and to est. the effective d. of states, D(EF). XPS and Raman microscopy were used to assess the compositional and structural properties as a function of nitrogen doping. XPS N1s spectra show three principle types of nitrogen coordination (pyridinic, pyrrolic, and quaternary). Raman was used as diagnostic tool for estg. the amt. of disorder by comparing D and G bands. A linear increase in the ratio of integrated D and G band intensities with nitrogen doping indicates that the amt. of disorder and no. of edge plane sites increase. Furthermore, D(EF) also increases with N doping and the amt. of disorder and no. of edge plane sites. UPS (UPS) was used to probe the valence band of N-CNTs in order to est. the work function of the mats. The work function increased linearly from 4.1 to 4.5 eV for increasing N-doping levels. The bulk elec. cond. of the N-CNT electrode mats appears to be junction dominated as shown by the relationship between the bulk cond. and av. N-CNT length within the mats detd. using high-resoln. scanning TEM (STEM). >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BD1MXht1CgtrrF&md5= 9bd2f88d84422695a5c46fa60b97f379 35. 35 Fabbri, E.; Habereder, A.; Waltar, K.; Kotz, R.; Schmidt, T. J. Developments and perspectives of oxide-based catalysts for the oxygen evolution reaction. Catal. Sci. Technol. 2014, 4, 3800- 3821, DOI: 10.1039/C4CY00669K [Crossref], [CAS], Google Scholar 35 Developments and perspectives of oxide-based catalysts for the oxygen evolution reaction Fabbri, E.; Habereder, A.; Waltar, K.; Kotz, R.; Schmidt, T. J. Catalysis Science & Technology (2014), 4 (11), 3800-3821CODEN: CSTAGD; ISSN:2044-4753. (Royal Society of Chemistry) A review. The growing need to store large amts. of energy produced from renewable sources has recently directed substantial R&D efforts towards water electrolysis technologies. Although the description of the electrochem. reaction of water electrolysis dates back to the late 18th century, improvements in terms of efficiency and stability are foreseen for a widespread market penetration of water electrolyzers. Particular advances are required for the electrode materials catalyzing the oxygen evolution reaction (OER) at the anode side, which has slow kinetics and thus is one of the major sources of the cell efficiency loss. In recent years, high-level theor. tools and computational studies have led to significant progress in the at.-level understanding of the OER and electrocatalyst behavior. In parallel, several exptl. studies have explored new catalytic materials with advanced properties and kinetics on a tech. relevant level. This contribution summarizes previous and the most recent theor. predictions and exptl. outcomes in the field of oxide-based catalysts for the OER, both operating in acidic and alk. environments. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtFWhs73K&md5= 1e03eaf45f961a58eb2c54e86d8c2b93 36. 36 Ekspong, J.; Wagberg, T. Stainless Steel as A Bi-Functional Electrocatalyst-A Top-Down Approach. Materials 2019, 12, 2128, DOI: 10.3390/ma12132128 [Crossref], [CAS], Google Scholar 36 Stainless steel as a bi-functional electrocatalyst-a top-down approach Ekspong, Joakim; Wagberg, Thomas Materials (2019), 12 (13), 2128CODEN: MATEG9; ISSN:1996-1944. ( MDPI AG) For a hydrogen economy to be viable, clean and economical hydrogen prodn. methods are vital. Electrolysis of water is a promising hydrogen prodn. technique with zero emissions, but suffer from relatively high prodn. costs. In order to make electrolysis of water sustainable, abundant, and efficient materials has to replace expensive and scarce noble metals as electrocatalysts in the reaction cells. Herein, we study activated stainless steel as a bi-functional electrocatalyst for the full water splitting reaction by taking advantage of nickel and iron suppressed within the bulk. The final electrocatalyst consists of a stainless steel mesh with a modified surface of layered NiFe nanosheets. By using a top down approach, the nanosheets stay well anchored to the surface and maintain an excellent elec. connection to the bulk structure. At ambient temp., the activated stainless steel electrodes produce 10 mA/cm2 at a cell voltage of 1.78 V and display an onset for water splitting at 1.68 V in 1M KOH, which is close to benchmarking nanosized catalysts. Furthermore, we use a scalable activation method using no externally added electrocatalyst, which could be a practical and cheap alternative to traditionally catalyst-coated electrodes. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BB3cXis1aqt7s%253D&md5= 0195f529ab8e35c5e8b73e72999733a2 37. 37 Gong, M. Nanoscale nickel oxide/nickel heterostructures for active hydrogen evolution electrocatalysis. Nat. Commun. 2014, 5, 4695, DOI: 10.1038/ncomms5695 [Crossref], [PubMed], [CAS], Google Scholar 37 Nanoscale nickel oxide/nickel heterostructures for active hydrogen evolution electrocatalysis Gong, Ming; Zhou, Wu; Tsai, Mon-Che; Zhou, Jigang; Guan, Mingyun; Lin, Meng-Chang; Zhang, Bo; Hu, Yongfeng; Wang, Di-Yan; Yang, Jiang; Pennycook, Stephen J.; Hwang, Bing-Joe; Dai, Hongjie Nature Communications (2014), 5 (), 4695CODEN: NCAOBW; ISSN: 2041-1723. (Nature Publishing Group) Active, stable and cost-effective electrocatalysts are a key to water splitting for hydrogen prodn. through electrolysis or photoelectrochem. Here we report nanoscale nickel oxide/nickel heterostructures formed on carbon nanotube sidewalls as highly effective electrocatalysts for hydrogen evolution reaction with activity similar to platinum. Partially reduced nickel interfaced with nickel oxide results from thermal decompn. of nickel hydroxide precursors bonded to carbon nanotube sidewalls. The metal ion-carbon nanotube interactions impede complete redn. and Ostwald ripening of nickel species into the less hydrogen evolution reaction active pure nickel phase. A water electrolyzer that achieves ~20 mA cm-2 at a voltage of 1.5 V, and which may be operated by a single-cell alk. battery, is fabricated using cheap, non-precious metal-based electrocatalysts. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2MXksVChtr8%253D&md5= 39664eecc487dbc1cf7fef21e874ec32 38. 38 Shinagawa, T.; Garcia-Esparza, A. T.; Takanabe, K. Insight on Tafel slopes from a microkinetic analysis of aqueous electrocatalysis for energy conversion. Sci. Rep. 2015, 5, 13801, DOI: 10.1038/srep13801 [Crossref], [PubMed], [CAS], Google Scholar 38 Insight on Tafel slopes from a microkinetic analysis of aqueous electrocatalysis for energy conversion Shinagawa Tatsuya; Garcia-Esparza Angel T; Takanabe Kazuhiro Scientific reports (2015), 5 (), 13801 ISSN:. Microkinetic analyses of aqueous electrochemistry involving gaseous H2 or O2, i.e., hydrogen evolution reaction (HER), hydrogen oxidation reaction (HOR), oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), are revisited. The Tafel slopes used to evaluate the rate determining steps generally assume extreme coverage of the adsorbed species (th[?]0 or [?]1), although, in practice, the slopes are coverage-dependent. We conducted detailed kinetic analyses describing the coverage-dependent Tafel slopes for the aforementioned reactions. Our careful analyses provide a general benchmark for experimentally observed Tafel slopes that can be assigned to specific rate determining steps. The Tafel analysis is a powerful tool for discussing the rate determining steps involved in electrocatalysis, but our study also demonstrated that overly simplified assumptions led to an inaccurate description of the surface electrocatalysis. Additionally, in many studies, Tafel analyses have been performed in conjunction with the Butler-Volmer equation, where its applicability regarding only electron transfer kinetics is often overlooked. Based on the derived kinetic description of the HER/HOR as an example, the limitation of Butler-Volmer expression in electrocatalysis is also discussed in this report. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A280%3ADC%252BC283gsFeluw%253D%253D&md5= ac27784a48ec67e4bea1ac3d6c62a416 39. 39 Ekspong, J.; Gracia-Espino, E.; Wagberg, T. Hydrogen Evolution Reaction Activity of Heterogeneous Materials: A Theoretical Model . J. Phys. Chem. C 2020, 124, 20911- 20921, DOI: 10.1021/ acs.jpcc.0c05243 [ACS Full Text ACS Full Text], [CAS], Google Scholar 39 Hydrogen Evolution Reaction Activity of Heterogeneous Materials: A Theoretical Model Ekspong, Joakim; Gracia-Espino, Eduardo; Waagberg, Thomas Journal of Physical Chemistry C (2020), 124 (38), 20911-20921 CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society) In this study, we present a new comprehensive methodol. to quantify the catalytic activity of heterogeneous materials for the hydrogen evolution reaction (HER) using ab initio simulations. The model is composed of two parts. First, the equil. hydrogen coverage is obtained by an iterative evaluation of the hydrogen adsorption free energies (DGH) using d. functional theory calcns. Afterward, the DGH are used in a microkinetic model to provide detailed characterizations of the entire HER considering all three elementary steps, i.e., the discharge, atom + ion, and combination reactions, without any prior assumptions of rate-detg. steps. The microkinetic model takes the equil. and potential-dependent characteristics into account, and thus both exchange current densities and Tafel slopes are evaluated. The model is tested on several systems, from polycryst. metals to heterogeneous molybdenum disulfide (MoS2), and by comparing to exptl. data, we verify that our model accurately predicts their exptl. exchange current densities and Tafel slopes. Finally, we present an extended volcano plot that correlates the elec. current densities of each elementary reaction step to the coverage-dependent DGH. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BB3cXhs1aqsL7N&md5= b344e1b4b9dc1a270294b4f8238ef72d 40. 40 Suen, N.-T. Electrocatalysis for the oxygen evolution reaction: recent development and future perspectives. Chem. Soc. Rev. 2017, 46, 337- 365, DOI: 10.1039/C6CS00328A [Crossref], [PubMed], [CAS], Google Scholar 40 Electrocatalysis for the oxygen evolution reaction: recent development and future perspectives Suen, Nian-Tzu; Hung, Sung-Fu; Quan, Quan; Zhang, Nan; Xu, Yi-Jun; Chen, Hao Ming Chemical Society Reviews (2017), 46 (2), 337-365CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry) There is still an ongoing effort to search for sustainable, clean and highly efficient energy generation to satisfy the energy needs of modern society. Among various advanced technologies, electrocatalysis for the oxygen evolution reaction (OER) plays a key role and numerous new electrocatalysts have been developed to improve the efficiency of gas evolution. Along the way, enormous effort has been devoted to finding high-performance electrocatalysts, which has also stimulated the invention of new techniques to investigate the properties of materials or the fundamental mechanism of the OER. This accumulated knowledge not only establishes the foundation of the mechanism of the OER, but also points out the important criteria for a good electrocatalyst based on a variety of studies. Even though it may be difficult to include all cases, the aim of this review is to inspect the current progress and offer a comprehensive insight toward the OER. This review begins with examg. the theor. principles of electrode kinetics and some measurement criteria for achieving a fair evaluation among the catalysts. The second part of this review acquaints some materials for performing OER activity, in which the metal oxide materials build the basis of OER mechanism while non-oxide materials exhibit greatly promising performance toward overall water-splitting. Attention of this review is also paid to in situ approaches to electrocatalytic behavior during OER, and this information is crucial and can provide efficient strategies to design perfect electrocatalysts for OER. Finally, the OER mechanism from the perspective of both recent exptl. and theor. investigations is discussed, as well as probable strategies for improving OER performance with regards to future developments. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2sXpslKksQ%253D%253D&md5= 3439b70760b2146baf20bddfa0447207 41. 41 Hall, D. S.; Lockwood, D. J.; Bock, C.; MacDougall, B. R. Nickel hydroxides and related materials: a review of their structures, synthesis and properties. Proc. R. Soc. London, Ser. A 2015, 471, 20140792, DOI: 10.1098/rspa.2014.0792 [Crossref], Google Scholar There is no corresponding record for this reference. 42. 42 Dionigi, F.; Strasser, P. NiFe-Based (Oxy)hydroxide Catalysts for Oxygen Evolution Reaction in Non-Acidic Electrolytes. Adv. Energy Mater. 2016, 6, 1600621, DOI: 10.1002/aenm.201600621 [Crossref], Google Scholar There is no corresponding record for this reference. 43. 43 Trotochaud, L.; Young, S. L.; Ranney, J. K.; Boettcher, S. W. Nickel-Iron Oxyhydroxide Oxygen-Evolution Electrocatalysts: The Role of Intentional and Incidental Iron Incorporation. J. Am. Chem. Soc. 2014, 136, 6744- 6753, DOI: 10.1021/ja502379c [ACS Full Text ACS Full Text], [CAS], Google Scholar 43 Nickel-Iron Oxyhydroxide Oxygen-Evolution Electrocatalysts: The Role of Intentional and Incidental Iron Incorporation Trotochaud, Lena; Young, Samantha L.; Ranney, James K.; Boettcher, Shannon W. Journal of the American Chemical Society (2014), 136 (18), 6744-6753CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society) Fe plays a crit., but not yet understood, role in enhancing the activity of the Ni-based O evolution reaction (OER) electrocatalysts. The authors report electrochem., in situ elec., photoelectron spectroscopy, and x-ray diffraction measurements on Ni1-xFex(OH)2/Ni1-xFexOOH thin films to study the changes in electronic properties, OER activity, and structure as a result of Fe inclusion. The authors developed a simple method for purifn. of KOH electrolyte that uses pptd. bulk Ni(OH)2 to absorb Fe impurities. Cyclic voltammetry on rigorously Fe-free Ni(OH)2/ NiOOH reveals new Ni redox features and no significant OER current until >400 mV overpotential, different from previous reports which were likely affected by Fe impurities. The authors show through controlled crystn. that b-NiOOH is less active for OER than the disordered g-NiOOH starting material and that previous reports of increased activity for b-NiOOH are due to incorporation of Fe-impurities during the crystn. process. Through-film in situ cond. measurements show a >30-fold increase in film cond. with Fe addn., but this change in cond. is not sufficient to explain the obsd. changes in activity. Measurements of activity as a function of film thickness on Au and glassy C substrates are consistent with the hypothesis that Fe exerts a partial-charge-transfer activation effect on Ni, similar to that obsd. for noble-metal electrode surfaces. These results have significant implications for the design and study of Ni1-xFexOOH OER electrocatalysts, which are the fastest measured OER catalysts under basic conditions. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2cXmtlygtLc%253D&md5= 6a26a961800255dfe91df6d95388f64d 44. 44 Costa, J. D. Electrocatalytic Performance and Stability of Nanostructured Fe-Ni Pyrite-Type Diphosphide Catalyst Supported on Carbon Paper. J. Phys. Chem. C 2016, 120, 16537- 16544, DOI: 10.1021/acs.jpcc.6b05783 [ACS Full Text ACS Full Text], Google Scholar There is no corresponding record for this reference. 45. 45 Kojima, A.; Teshima, K.; Shirai, Y.; Miyasaka, T. Organometal halide perovskites as visible-light sensitizers for photovoltaic cells. J. Am. Chem. Soc. 2009, 131, 6050- 6051, DOI: 10.1021/ ja809598r [ACS Full Text ACS Full Text], [CAS], Google Scholar 45 Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells Kojima, Akihiro; Teshima, Kenjiro; Shirai, Yasuo; Miyasaka, Tsutomu Journal of the American Chemical Society (2009), 131 (17), 6050-6051CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society) Two organolead halide perovskite nanocrystals, MeNH3PbBr3 and MeNH3PbI3, efficiently sensitize TiO2 for visible-light conversion in photoelectrochem. cells. When self-assembled on mesoporous TiO2 films, the nanocryst. perovskites exhibit strong band-gap absorptions as semiconductors. The MeNH3PbI3-based photocell with spectral sensitivity of up to 800 nm yielded a solar energy conversion efficiency of 3.8%. The MeNH3PbBr3-based cell showed a high photovoltage of 0.96 V with an external quantum conversion efficiency of 65%. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BD1MXksV2iurc%253D&md5= fc3cee6cc3a6955da4fe9e344fdcd3b9 46. 46 Lee, M. M.; Teuscher, J.; Miyasaka, T.; Murakami, T. N.; Snaith, H. J. Efficient hybrid solar cells based on meso-superstructured organometal halide perovskites. Science 2012, 338, 643- 647, DOI: 10.1126/science.1228604 [Crossref], [PubMed], [CAS], Google Scholar 46 Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites Lee, Michael M.; Teuscher, Joel; Miyasaka, Tsutomu; Murakami, Takurou N.; Snaith, Henry J. Science (Washington, DC, United States) (2012), 338 (6107), 643-647CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science) The energy costs assocd. with sepg. tightly bound excitons (photoinduced electron-hole pairs) and extg. free charges from highly disordered low-mobility networks represent fundamental losses for many low-cost photovoltaic technologies. A low-cost, soln.-processable solar cell is reported, based on a highly cryst. perovskite absorber with intense visible to near-IR absorptivity, that has a power conversion efficiency of 10.9% in a single-junction device under simulated full sunlight. This "meso-superstructured solar cell" exhibits exceptionally few fundamental energy losses; it can generate open-circuit photovoltages of more than 1.1 V, despite the relatively narrow absorber band gap of 1.55 eV. The functionality arises from the use of mesoporous alumina as an inert scaffold that structures the absorber and forces electrons to reside in and be transported through the perovskite. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC38XhsFygtbrL&md5= fdddb80f46817da2f0d11f6434746226 47. 47 Burschka, J. Sequential deposition as a route to high-performance perovskite-sensitized solar cells. Nature 2013, 499, 316- 319, DOI: 10.1038/nature12340 [Crossref], [PubMed], [CAS], Google Scholar 47 Sequential deposition as a route to high-performance perovskite-sensitized solar cells Burschka, Julian; Pellet, Norman; Moon, Soo-Jin; Humphry-Baker, Robin; Gao, Peng; Nazeeruddin, Mohammad K.; Graetzel, Michael Nature (London, United Kingdom) (2013), 499 (7458), 316-319CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group) Following pioneering work, soln.-processable org.-inorg. hybrid perovskites-such as CH3NH3PbX3 (X = Cl, Br, I)-have attracted attention as light-harvesting materials for mesoscopic solar cells. So far, the perovskite pigment has been deposited in a single step onto mesoporous metal oxide films using a mixt. of PbX2 and CH3NH3X in a common solvent. However, the uncontrolled pptn. of the perovskite produces large morphol. variations, resulting in a wide spread of photovoltaic performance in the resulting devices, which hampers the prospects for practical applications. Here we describe a sequential deposition method for the formation of the perovskite pigment within the porous metal oxide film. PbI2 is first introduced from soln. into a nanoporous titanium dioxide film and subsequently transformed into the perovskite by exposing it to a soln. of CH3NH3I. We find that the conversion occurs within the nanoporous host as soon as the two components come into contact, permitting much better control over the perovskite morphol. than is possible with the previously employed route. Using this technique for the fabrication of solid-state mesoscopic solar cells greatly increases the reproducibility of their performance and allows us to achieve a power conversion efficiency of approx. 15 per cent (measured under std. AM1.5G test conditions on solar zenith angle, solar light intensity and cell temp.). This two-step method should provide new opportunities for the fabrication of soln.-processed photovoltaic cells with unprecedented power conversion efficiencies and high stability equal to or even greater than those of today's best thin-film photovoltaic devices. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFShtbzL&md5= d00fae216daa9b428f9d38d97d7e2079 48. 48 Nocera, D. G. The artificial leaf. Acc. Chem. Res. 2012, 45, 767- 776, DOI: 10.1021/ar2003013 [ACS Full Text ACS Full Text], [CAS], Google Scholar 48 The Artificial Leaf Nocera, Daniel G. Accounts of Chemical Research (2012), 45 (5), 767-776CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society) A review. To convert the energy of sunlight into chem. energy, the leaf splits H2O via the photosynthetic process to produce mol. O and H, which is in a form of sepd. protons and electrons. The primary steps of natural photosynthesis involve the absorption of sunlight and its conversion into spatially sepd. electron-hole pairs. The holes of this wireless current are captured by the O evolving complex (OEC) of photosystem II (PSII) to oxidize H2O to O. The electrons and protons produced as a byproduct of the OEC reaction are captured by ferrodoxin of photosystem I. With the aid of ferrodoxin-NADP+ reductase, they are used to produce H as NADPH. For a synthetic material to realize the solar energy conversion function of the leaf, the light-absorbing material must capture a solar photon to generate a wireless current that is harnessed by catalysts, which drive the 4 electron/hole fuel-forming H2O-splitting reaction under benign conditions and under 1 sun (100 mW/cm2) illumination. This Account describes the construction of an artificial leaf comprising earth-abundant elements by interfacing a triple junction, amorphous Si photovoltaic with H- and O-evolving catalysts made from a ternary alloy (NiMoZn) and a Co-phosphate cluster (Co-OEC), resp. The latter captures the structural and functional attributes of the PSII-OEC. Similar to the PSII-OEC, the Co-OEC self-assembles upon oxidn. of an earth-abundant metal ion from 2+ to 3+, may operate in natural H2O at room temp., and is self-healing. The Co-OEC also activates H2O by a p-coupled electron transfer mechanism in which the Co-OEC is increased by 4 hole equiv. akin to the S-state pumping of the Kok cycle of PSII. X-ray absorption spectroscopy studies established that the Co-OEC is a structural relative of Mn3CaO4-Mn cubane of the PSII-OEC, where Co replaces Mn and the cubane is extended in a corner-sharing, head-to-tail dimer. The ability to perform the O-evolving reaction in H2O at neutral or near-neutral conditions has several consequences for the construction of the artificial leaf. The NiMoZn alloy may be used in place of Pt to generate H. To stabilize Si in H2O, its surface is coated with a conducting metal oxide onto which the Co-OEC may be deposited. The net result is that immersing a triple-junction Si wafer coated with NiMoZn and Co-OEC in H2O and holding it up to sunlight can effect direct solar energy conversion via H2O splitting. By constructing a simple, stand-alone device composed of earth-abundant materials, the artificial leaf provides a means for an inexpensive and highly distributed solar-to-fuels system that employs low-cost systems engineering and manufg. Through this type of system, solar energy can become a viable energy supply to those in the non-legacy world. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC38XltVylu7k%253D&md5= c7ae917b44e8c4be8a38bf2be8f384d0 49. 49 Reece, S. Y. Wireless solar water splitting using silicon-based semiconductors and earth-abundant catalysts. Science 2011, 334, 645- 648, DOI: 10.1126/science.1209816 [Crossref], [PubMed], [CAS], Google Scholar 49 Wireless Solar Water Splitting Using Silicon-Based Semiconductors and Earth-Abundant Catalysts Reece, Steven Y.; Hamel, Jonathan A.; Sung, Kimberly; Jarvi, Thomas D.; Esswein, Arthur J.; Pijpers, Joep J. H.; Nocera, Daniel G. Science (Washington, DC, United States) (2011), 334 (6056), 645-648CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science) We describe the development of solar water-splitting cells comprising earth-abundant elements that operate in near-neutral pH conditions, both with and without connecting wires. The cells consist of a triple junction, amorphous silicon photovoltaic interfaced to hydrogen- and oxygen-evolving catalysts made from an alloy of earth-abundant metals and a cobalt-borate catalyst, resp. The devices described here carry out the solar-driven water-splitting reaction at efficiencies of 4.7% for a wired configuration and 2.5% for a wireless configuration when illuminated with 1 sun (100 mW per square centimeter) of air mass 1.5 simulated sunlight. Fuel-forming catalysts interfaced with light-harvesting semiconductors afford a pathway to direct solar-to-fuels conversion that captures many of the basic functional elements of a leaf. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtlyqu7vF&md5= f7bb658892c9c78d7a9d8f011c73a7b1 50. 50 Sharifi, T. Toward a Low-Cost Artificial Leaf: Driving Carbon-Based and Bifunctional Catalyst Electrodes with Solution-Processed Perovskite Photovoltaics. Adv. Energy Mater. 2016, 6, 1600738, DOI: 10.1002/aenm.201600738 [Crossref], Google Scholar There is no corresponding record for this reference. 51. 51 Li, Z. Hybrid Perovskite-Organic Flexible Tandem Solar Cell Enabling Highly Efficient Electrocatalysis Overall Water Splitting. Adv. Energy Mater. 2020, 10, 2000361, DOI: 10.1002/ aenm.202000361 [Crossref], [CAS], Google Scholar 51 Hybrid Perovskite-Organic Flexible Tandem Solar Cell Enabling Highly Efficient Electrocatalysis Overall Water Splitting Li, Zhen; Wu, Shengfan; Zhang, Jie; Lee, Ka Chun; Lei, Hang; Lin, Francis; Wang, Zilong; Zhu, Zonglong; Jen, Alex K. Y. Advanced Energy Materials (2020), 10 (18), 2000361CODEN: ADEMBC; ISSN:1614-6840. (Wiley-Blackwell) Perovskite-org. tandem solar cells are attracting more attention due to their potential for highly efficient and flexible photovoltaic device. In this work, efficient perovskite-org. monolithic tandem solar cells integrating the wide bandgap perovskite (1.74 eV) and low bandgap org. active PBDB-T:SN6IC-4F (1.30 eV) layer, which serve as the top and bottom subcell, resp., are developed. The resulting perovskite-org. tandem solar cells with passivated wide-bandgap perovskite show a remarkable power conversion efficiency (PCE) of 15.13%, with an open-circuit voltage (Voc) of 1.85 V, a short-circuit photocurrent (Jsc) of 11.52 mA cm-2, and a fill factor (FF) of 70.98%. Thanks to the advantages of low temp. fabrication processes and the flexibility properties of the device, a flexible tandem solar cell which obtain a PCE of 13.61%, with Voc of 1.80 V, Jsc of 11.07 mA cm-2, and FF of 68.31% is fabricated. Moreover, to demonstrate the achieved high Voc in the tandem solar cells for potential applications, a photovoltaic (PV)-driven electrolysis system combing the tandem solar cell and water splitting electrocatalysis is assembled. The integrated device demonstrates a solar-to-hydrogen efficiency of 12.30% and 11.21% for rigid, and flexible perovskite-org. tandem solar cell based PV-driven electrolysis systems, resp. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BB3cXlt1ChtLk%253D&md5= e13b988660194a3ace033622a339a576 52. 52 Karuturi, S. K. Over 17% Efficiency Stand-Alone Solar Water Splitting Enabled by Perovskite-Silicon Tandem Absorbers. Adv. Energy Mater. 2020, 10, 2000772, DOI: 10.1002/aenm.202000772 [Crossref], [CAS], Google Scholar 52 Over 17% Efficiency Stand-Alone Solar Water Splitting Enabled by Perovskite-Silicon Tandem Absorbers Karuturi, Siva Krishna; Shen, Heping; Sharma, Astha; Beck, Fiona J.; Varadhan, Purushothaman; Duong, The; Narangari, Parvathala Reddy; Zhang, Doudou; Wan, Yimao; He, Jr-Hau; Tan, Hark Hoe; Jagadish, Chennupati; Catchpole, Kylie Advanced Energy Materials (2020), 10 (28), 2000772CODEN: ADEMBC; ISSN:1614-6840. (Wiley-Blackwell) Realizing solar-to-hydrogen (STH) efficiencies close to 20% using low-cost semiconductors remains a major step toward accomplishing the practical viability of photoelectrochem. (PEC) hydrogen generation technologies. Dual-absorber tandem cells combining inexpensive semiconductors are a promising strategy to achieve high STH efficiencies at a reasonable cost. Here, a perovskite photovoltaic biased silicon (Si) photoelectrode is demonstrated for highly efficient stand-alone solar water splitting. A p+nn+ -Si/Ti/Pt photocathode is shown to present a remarkable photon-to-current efficiency of 14.1% under biased condition and stability over three days under continuous illumination. Upon pairing with a semitransparent mixed perovskite solar cell of an appropriate bandgap with state-of-the-art performance, an unprecedented 17.6% STH efficiency is achieved for self-driven solar water splitting. Modeling and anal. of the dual-absorber PEC system reveal that further work into replacing the noble-metal catalyst materials with earth-abundant elements and improvement of perovskite fill factor will pave the way for the realization of a low-cost high-efficiency PEC system. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtFCis7jM&md5= c44743dde681fa5593e1e9ee9d773274 53. 53 Luo, J. Water photolysis at 12.3% efficiency via perovskite photovoltaics and Earth-abundant catalysts. Science 2014, 345, 1593- 1596, DOI: 10.1126/science.1258307 [Crossref], [PubMed], [CAS], Google Scholar 53 Water photolysis at 12.3% efficiency via perovskite photovoltaics and Earth-abundant catalysts Luo, Jingshan; Im, Jeong-Hyeok; Mayer, Matthew T.; Schreier, Marcel; Nazeeruddin, Mohammad Khaja; Park, Nam-Gyu; Tilley, S. David; Fan, Hong Jin; Graetzel, Michael Science (Washington, DC, United States) (2014), 345 (6204), 1593-1596CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science) Although sunlight-driven H2O splitting is a promising route to sustainable H fuel prodn., widespread implementation is hampered by the expense of the necessary photovoltaic and photoelectrochem. app. Here, the authors describe a highly efficient and low-cost H2O-splitting cell combining a state-of-the-art soln.-processed perovskite tandem solar cell and a bifunctional Earth-abundant catalyst. The catalyst electrode, a NiFe layered double hydroxide, exhibits high activity toward both the O and H evolution reactions in alk. electrolyte. The combination of the 2 yields a H2O-splitting photocurrent d. of ~10 mA per square centimeter, corresponding to a solar-to-H efficiency of 12.3%. Currently, the perovskite instability limits the cell lifetime. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2cXhsFygtbbJ&md5= 2db34619748164992665db7ab6b53914 54. 54 Luo, J. Bipolar Membrane-Assisted Solar Water Splitting in Optimal pH. Adv. Energy Mater. 2016, 6, 1600100, DOI: 10.1002/ aenm.201600100 [Crossref], Google Scholar There is no corresponding record for this reference. 55. 55 Zou, X.; Zhang, Y. Noble metal-free hydrogen evolution catalysts for water splitting. Chem. Soc. Rev. 2015, 44, 5148- 5180, DOI: 10.1039/C4CS00448E [Crossref], [PubMed], [CAS], Google Scholar 55 Noble metal-free hydrogen evolution catalysts for water splitting Zou, Xiaoxin; Zhang, Yu Chemical Society Reviews (2015), 44 (15), 5148-5180CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry) Sustainable hydrogen prodn. is an essential prerequisite of a future hydrogen economy. Water electrolysis driven by renewable resource-derived electricity and direct solar-to-hydrogen conversion based on photochem. and photoelectrochem. water splitting are promising pathways for sustainable hydrogen prodn. All these techniques require, among many things, highly active noble metal-free hydrogen evolution catalysts to make the water splitting process more energy-efficient and economical. In this review, we highlight the recent research efforts toward the synthesis of noble metal-free electrocatalysts, esp. at the nanoscale, and their catalytic properties for the hydrogen evolution reaction (HER). We review several important kinds of heterogeneous non-precious metal electrocatalysts, including metal sulfides, metal selenides, metal carbides, metal nitrides, metal phosphides, and heteroatom-doped nanocarbons. In the discussion, emphasis is given to the synthetic methods of these HER electrocatalysts, the strategies of performance improvement, and the structure/compn.-catalytic activity relationship. We also summarize some important examples showing that non-Pt HER electrocatalysts could serve as efficient cocatalysts for promoting direct solar-to-hydrogen conversion in both photochem. and photoelectrochem. water splitting systems, when combined with suitable semiconductor photocatalysts. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2MXms1ygtbo%253D&md5= ac5b0a548bab69f1e7a05520c8f1ced2 56. 56 Boyd, C. C.; Cheacharoen, R.; Leijtens, T.; McGehee, M. D. Understanding Degradation Mechanisms and Improving Stability of Perovskite Photovoltaics. Chem. Rev. 2019, 119, 3418- 3451, DOI: 10.1021/acs.chemrev.8b00336 [ACS Full Text ACS Full Text], [CAS], Google Scholar 56 Understanding Degradation Mechanisms and Improving Stability of Perovskite Photovoltaics Boyd, Caleb C.; Cheacharoen, Rongrong; Leijtens, Tomas; McGehee, Michael D. Chemical Reviews (Washington, DC, United States) (2019), 119 (5), 3418-3451CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society) This review article examines the current state of understanding in how metal halide perovskite solar cells can degrade when exposed to moisture, oxygen, heat, light, mech. stress, and reverse bias. It also highlights strategies for improving stability, such as tuning the compn. of the perovskite, introducing hydrophobic coatings, replacing metal electrodes with carbon or transparent conducting oxides, and packaging. The article concludes with recommendations on how accelerated testing should be performed to rapidly develop solar cells that are both extraordinarily efficient and stable. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC1cXit1Smt7fL&md5= 31d99d3f1b29ccacdba83624b84b3c54 57. 57 Juarez-Perez, E. J. Photodecomposition and thermal decomposition in methylammonium halide lead perovskites and inferred design principles to increase photovoltaic device stability. J. Mater. Chem. A 2018, 6, 9604- 9612, DOI: 10.1039/C8TA03501F [Crossref], [CAS], Google Scholar 57 Photodecomposition and thermal decomposition in methylammonium halide lead perovskites and inferred design principles to increase photovoltaic device stability Juarez-Perez, Emilio J.; Ono, Luis K.; Maeda, Maki; Jiang, Yan; Hawash, Zafer; Qi, Yabing Journal of Materials Chemistry A: Materials for Energy and Sustainability (2018), 6 (20), 9604-9612CODEN: JMCAET; ISSN: 2050-7496. (Royal Society of Chemistry) Hybrid lead halide perovskites have emerged as promising active materials for photovoltaic cells. Although superb efficiencies have been achieved, it is widely recognized that long-term stability is a key challenge intimately detg. the future development of perovskite-based photovoltaic technol. Herein, we present reversible and irreversible photodecompn. reactions of methylammonium lead iodide (MAPbI3). Simulated sunlight irradn. and temp. (40-80 degC) corresponding to solar cell working conditions lead to three degrdn. pathways: (1) CH3NH2 + HI (identified as the reversible path), (2) NH3 + CH3I (the irreversible or detrimental path), and (3) a reversible Pb(0) + I2(g) photodecompn. reaction. If only the reversible reactions (1) and (3) take place and reaction (2) can be avoided, encapsulated MAPbI3 can be regenerated during the off-illumination timeframe. Therefore, to further improve operational stability in hybrid perovskite solar cells, detailed understanding of how to mitigate photodegrdn. and thermal degrdn. processes is necessary. First, encapsulation of the device is necessary not only to avoid contact of the perovskite with ambient air, but also to prevent leakage of volatile products released from the perovskite. Second, careful selection of the org. cations in the compositional formula of the perovskite is necessary to avoid irreversible reactions. Third, selective contacts must be as chem. inert as possible toward the volatile released products. Finally, hybrid halide perovskite materials are speculated to undergo a dynamic formation and decompn. process; this can gradually decrease the cryst. grain size of the perovskite with time; therefore, efforts to deposit highly cryst. perovskites with large crystal sizes may fail to increase the long-term stability of photovoltaic devices. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC1cXotF2isrY%253D&md5= d336b7d9a747eec1e988e066cd7ab159 58. 58 Ciccioli, A.; Latini, A. Thermodynamics and the Intrinsic Stability of Lead Halide Perovskites CH3NH3PbX3. J. Phys. Chem. Lett. 2018, 9, 3756- 3765, DOI: 10.1021/acs.jpclett.8b00463 [ACS Full Text ACS Full Text], [CAS], Google Scholar 58 Thermodynamics and the Intrinsic Stability of Lead Halide Perovskites CH3NH3PbX3 Ciccioli, Andrea; Latini, Alessandro Journal of Physical Chemistry Letters (2018), 9 (13), 3756-3765 CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society) The role of thermodn. in assessing the intrinsic instability of the MeNH3PbX3 perovskites (X = Cl,Br,I) is outlined from the available exptl. information. Possible decompn./degrdn. pathways driven by the inherent instability of the material are considered. The decompn. to precursors MeNH3X(s) and PbX2(s) is 1st analyzed, pointing out the importance of both the enthalpic and the entropic factor, the latter playing a stabilizing role making the stability higher than often asserted. For MeNH3PbI3, the disagreement between the available calorimetric results makes the stability prediction uncertain. Subsequently, the gas-releasing decompn. paths are discussed, with emphasis on the discrepant results presently available, probably reflecting the predominance of thermodn. or kinetic control. The competition between the formation of NH3(g) + MeX(g), MeNH2(g) + HX(g) or MeNH3X(g) is analyzed, in comparison with the thermal decompn. of methylammonium halides. In view of the scarce and inconclusive thermodn. studies to-date available, the need for further exptl. data is emphasized. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtFeisrvI&md5= 58763d57fdcef06be34aa2834609ef14 59. 59 Samu, G. F.; Janaky, C.; Kamat, P. V. A Victim of Halide Ion Segregation. How Light Soaking Affects Solar Cell Performance of Mixed Halide Lead Perovskites. ACS Energy Letters 2017, 2, 1860- 1861, DOI: 10.1021/acsenergylett.7b00589 [ACS Full Text ACS Full Text], [CAS], Google Scholar 59 A Victim of Halide Ion Segregation. How Light Soaking Affects Solar Cell Performance of Mixed Halide Lead Perovskites Samu, Gergely F.; Janaky, Csaba; Kamat, Prashant V. ACS Energy Letters (2017), 2 (8), 1860-1861CODEN: AELCCP; ISSN: 2380-8195. (American Chemical Society) Photoinduced segregation in mixed halide perovskites has a direct influence on decreasing the solar cell efficiency as segregated I-rich domains serve as charge recombination centers. The changes in the external quantum efficiency mirror the spectral loss in the absorption; however, the time scale of the IPCE recovery in the dark is slower than the absorption recovery, showing the intricate nature of the photoinduced halide segregation and charge collection in solar cell devices. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2sXht1Wku7bP&md5= 023d6b709c4c9cd1b91e2b90d7c4acc3 60. 60 Latini, A.; Gigli, G.; Ciccioli, A. A study on the nature of the thermal decomposition of methylammonium lead iodide perovskite, CH3NH3PbI3: an attempt to rationalise contradictory experimental results. Sustainable Energy & Fuels 2017, 1, 1351- 1357, DOI: 10.1039/C7SE00114B [Crossref], [CAS], Google Scholar 60 A study on the nature of the thermal decomposition of methylammonium lead iodide perovskite, CH3NH3PbI3: an attempt to rationalise contradictory experimental results Latini, Alessandro; Gigli, Guido; Ciccioli, Andrea Sustainable Energy & Fuels (2017), 1 (6), 1351-1357CODEN: SEFUA7; ISSN:2398-4902. (Royal Society of Chemistry) The nature of the gas phase product released during the thermal decompn. of CH3NH3PbI3 (methylammonium lead iodide) to PbI2 (lead diiodide) under vacuum is discussed on the basis of thermodn. predictions, recently published exptl. results, and new expts. presented here. From the limited data currently available, the nature of the main decompn. path is not clear because, both, the process releasing HI(g) + CH3NH2(g) and that leading to NH3(g) + CH3I(g) were obsd. under different conditions. Our thermodn. anal. showed that process is largely favored for all the CH3NH3PbX3 (X = Cl, Br, I) compds. However, Knudsen effusion mass spectrometry expts. (temp. range 140-240 degC) showed that HI(g) and CH3NH2(g) were the predominant species in the vapor, with process occurring to a much smaller extent than suggested by the thermodn. driving force, thus being of minor importance under effusion conditions. We also found that this process was comparatively enhanced by high temps. and low effusion rates (high impedance orifice). Our exptl. evidence suggested that the thermodynamically favored process was affected by a significant kinetic hindrance. Overall, the prevailing decompn. path is likely to markedly depend on the actual operative conditions. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2sXhs1CrsLrL&md5= c942e4c428cd439c6f0d65b304522ea2 61. 61 Shao, Y. Grain boundary dominated ion migration in polycrystalline organic-inorganic halide perovskite films. Energy Environ. Sci. 2016, 9, 1752- 1759, DOI: 10.1039/C6EE00413J [Crossref], [CAS], Google Scholar 61 Grain boundary dominated ion migration in polycrystalline organic-inorganic halide perovskite films Shao, Yuchuan; Fang, Yanjun; Li, Tao; Wang, Qi; Dong, Qingfeng; Deng, Yehao; Yuan, Yongbo; Wei, Haotong; Wang, Meiyu; Gruverman, Alexei; Shield, Jeffery; Huang, Jinsong Energy & Environmental Science (2016), 9 (5), 1752-1759CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry) The efficiency of perovskite solar cells is approaching that of single-cryst. silicon solar cells despite the presence of a large grain boundary (GB) area in the polycryst. thin films. Here, by using a combination of nanoscopic and macroscopic level measurements, we show that ion migration in polycryst. perovskites dominates through GBs. Atomic force microscopy measurements reveal much stronger hysteresis both for photocurrent and dark-current at the GBs than on the grain interiors, which can be explained by faster ion migration at the GBs. The dramatically enhanced ion migration results in the redistribution of ions along the GBs after elec. poling, in contrast to the intact grain area. The perovskite single-crystal devices without GBs show negligible current hysteresis and no ion-migration signal. The discovery of dominating ion migration through GBs in perovskites can lead to broad applications in many types of devices including photovoltaics, memristors, and ion batteries. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC28XksFKmsrc%253D&md5= 134dde4b7e9fae67f7d845a8918d30f5 62. 62 Juarez-Perez, E. J.; Hawash, Z.; Raga, S. R.; Ono, L. K.; Qi, Y. Thermal degradation of CH3NH3PbI3 perovskite into NH3 and CH3I gases observed by coupled thermogravimetry-mass spectrometry analysis. Energy Environ. Sci. 2016, 9, 3406- 3410, DOI: 10.1039 /C6EE02016J [Crossref], [CAS], Google Scholar 62 Thermal degradation of CH3NH3PbI3 perovskite into NH3 and CH3I gases observed by coupled thermogravimetry-mass spectrometry analysis Juarez-Perez, Emilio J.; Hawash, Zafer; Raga, Sonia R.; Ono, Luis K.; Qi, Yabing Energy & Environmental Science (2016), 9 (11), 3406-3410CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry) Thermal gravimetric and DTA (TG-DTA) coupled with quadrupole mass spectrometry (MS) and first principles calcns. were employed to elucidate the chem. nature of released gases during the thermal decompn. of CH3NH3PbI3. In contrast to the common wisdom that CH3NH3PbI3 is decompd. into CH3NH2 and HI, the major gases were methyliodide (CH3I) and ammonia (NH3). We anticipate that our findings will provide new insights into further formulations of the perovskite active material and device design that can prevent methylammonium decompn. and thus increase the long-term stability of perovskite-based optoelectronic devices. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC28XhsVKjtLjM&md5= c6c03d9dbf93e71a54a56d5cf9d7f000 63. 63 Brunetti, B.; Cavallo, C.; Ciccioli, A.; Gigli, G.; Latini, A. On the Thermal and Thermodynamic (In)Stability of Methylammonium Lead Halide Perovskites. Sci. Rep. 2016, 6, 31896, DOI: 10.1038/ srep31896 [Crossref], [PubMed], [CAS], Google Scholar 63 On the Thermal and Thermodynamic (In)Stability of Methylammonium Lead Halide Perovskites Brunetti, Bruno; Cavallo, Carmen; Ciccioli, Andrea; Gigli, Guido; Latini, Alessandro Scientific Reports (2016), 6 (), 31896CODEN: SRCEC3; ISSN: 2045-2322. (Nature Publishing Group) The interest of the scientific community on methylammonium lead halide perovskites (MAPbX3, X = Cl, Br, I) for hybrid org.-inorg. solar cells has grown exponentially since the first report in 2009. This fact is clearly justified by the very high efficiencies attainable (reaching 20% in lab scale devices) at a fraction of the cost of conventional photovoltaics. However, many problems must be solved before a market introduction of these devices can be envisaged. Perhaps the most important to be addressed is the lack of information regarding the thermal and thermodn. stability of the materials towards decompn., which are intrinsic properties of them and which can seriously limit or even exclude their use in real devices. In this work we present and discuss the results we obtained using non-ambient X-ray diffraction, Knudsen effusion-mass spectrometry (KEMS) and Knudsen effusion mass loss (KEML) techniques on MAPbCl3, MAPbBr3 and MAPbI3. The measurements demonstrate that all the materials decomp. to the corresponding solid lead (II) halide and gaseous methylamine and hydrogen halide, and the decompn. is well detectable even at moderate temps. (~60 degC). Our results suggest that these materials may be problematic for long term operation of solar devices. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC28XhsVSrsb7N&md5= 531e2461d5fd57c414ad5d9959bbd25c 64. 64 Zhang, Y. Charge selective contacts, mobile ions and anomalous hysteresis in organic-inorganic perovskite solar cells. Mater. Horiz. 2015, 2, 315- 322, DOI: 10.1039/C4MH00238E [Crossref], [CAS], Google Scholar 64 Charge selective contacts, mobile ions and anomalous hysteresis in organic-inorganic perovskite solar cells Zhang, Ye; Liu, Mingzhen; Eperon, Giles E.; Leijtens, Tomas C.; McMeekin, David; Saliba, Michael; Zhang, Wei; de Bastiani, Michele; Petrozza, Annamaria; Herz, Laura M.; Johnston, Michael B.; Lin, Hong; Snaith, Henry J. Materials Horizons (2015), 2 (3), 315-322CODEN: MHAOBM; ISSN: 2051-6355. (Royal Society of Chemistry) High-efficiency perovskite solar cells typically employ an org.-inorg. metal halide perovskite material as light absorber and charge transporter, sandwiched between a p-type electron-blocking org. hole-transporting layer and an n-type hole-blocking electron collection titania compact layer. Some device configurations also include a thin mesoporous layer of TiO2 or Al2O3 which is infiltrated and capped with the perovskite absorber. Herein, we demonstrate that it is possible to fabricate planar and mesoporous perovskite solar cells devoid of an electron selective hole-blocking titania compact layer, which momentarily exhibit power conversion efficiencies (PCEs) of over 13%. This performance is however not sustained and is related to the previously obsd. anomalous hysteresis in perovskite solar cells. The "compact layer-free" meso-superstructured perovskite devices yield a stabilized PCE of only 2.7% while the compact layer-free planar heterojunction devices display no measurable steady state power output when devoid of an electron selective contact. In contrast, devices including the titania compact layer exhibit stabilized efficiency close to that derived from the current voltage measurements. We propose that under forward bias the perovskite diode becomes polarised, providing a beneficial field, allowing accumulation of pos. and neg. space charge near the contacts, which enables more efficient charge extn. This provides the required built-in potential and selective charge extn. at each contact to temporarily enable efficient operation of the perovskite solar cells even in the absence of charge selective n- and p-type contact layers. The polarisation of the material is consistent with long range migration and accumulation of ionic species within the perovskite to the regions near the contacts. When the external field is reduced under working conditions, the ions can slowly diffuse away from the contacts redistributing throughout the film, reducing the field asymmetry and the effectiveness of the operation of the solar cells. We note that in light of recent publications showing high efficiency in devices devoid of charge. selective contacts, this work reaffirms the abs. necessity to measure and report the stabilized power output under load when characterizing perovskite solar cells. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2MXjs1Kntb8%253D&md5= 3af138d227ee0f69d7e253ee29d8732e 65. 65 Han, Y. Degradation observations of encapsulated planar CH3NH3PbI3 perovskite solar cells at high temperatures and humidity. J. Mater. Chem. A 2015, 3, 8139- 8147, DOI: 10.1039/ C5TA00358J [Crossref], [CAS], Google Scholar 65 Degradation observations of encapsulated planar CH3NH3PbI3 perovskite solar cells at high temperatures and humidity Han, Yu; Meyer, Steffen; Dkhissi, Yasmina; Weber, Karl; Pringle, Jennifer M.; Bach, Udo; Spiccia, Leone; Cheng, Yi-Bing Journal of Materials Chemistry A: Materials for Energy and Sustainability (2015), 3 (15), 8139-8147CODEN: JMCAET; ISSN: 2050-7496. (Royal Society of Chemistry) The stability of encapsulated planar-structured CH3NH3PbI3 (MAPbI3) perovskite solar cells (PSCs) was investigated under various simulated environmental conditions. The tests were performed under approx. one sun (100 mW cm-2) illumination, varying temp. (up to 85 degC cell temp.) and humidity (up to 80%). The application of advanced sealing techniques improved the device stability, but all devices showed significant degrdn. after prolonged aging at high temp. and humidity. The degrdn. mechanism was studied by post-mortem anal. of the disassembled cells using SEM and XRD. This revealed that the degrdn. was mainly due to the decompn. of MAPbI3, as a result of reaction with H2O, and the subsequent reaction of hydroiodic acid, formed during MAPbI3 decompn., with the silver back contact electrode layer. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2MXjvF2ktLo%253D&md5= eeb439adec1eafcc54e12bb16726305a 66. 66 Azpiroz, J. M.; Mosconi, E.; Bisquert, J.; De Angelis, F. Defect migration in methylammonium lead iodide and its role in perovskite solar cell operation. Energy Environ. Sci. 2015, 8, 2118- 2127, DOI: 10.1039/C5EE01265A [Crossref], [CAS], Google Scholar 66 Defect migration in methylammonium lead iodide and its role in perovskite solar cell operation Azpiroz, Jon M.; Mosconi, Edoardo; Bisquert, Juan; De Angelis, Filippo Energy & Environmental Science (2015), 8 (7), 2118-2127CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry) In spite of the unprecedented advance of organohalide lead perovskites in the photovoltaics scenario, many of the characteristics of this class of materials, including their slow photocond. response, solar cell hysteresis, and switchable photocurrent, remain poorly understood. Many exptl. hints point to defect migration as a plausible mechanism underlying these anomalous properties. By means of state-of-the-art first-principles computational analyses carried out on the tetragonal MAPbI3 (MA = methylammonium) perovskite and on its interface with TiO2, we demonstrate that iodine vacancies and interstitials may easily diffuse across the perovskite crystal, with migration activation energies as low as ~0.1 eV. Under working conditions, iodine-related defects are predicted to migrate at the electrodes on very short time scales (<1 ms). MA and Pb vacancies, with calcd. activation barriers of ~0.5 and 0.8 eV, resp., could be responsible for the slow response inherent to perovskites, with typical calcd. migration times of the order of tens of ms to minutes. By investigating realistic models of the perovskite/TiO2 interface we show that neg. charged defects, e.g. MA vacancies, close to the electron transport layer (TiO2 in our case) modify the perovskite electronic state landscape, hampering charge extn. at selective contacts, thus possibly contributing to the obsd. solar cell hysteresis. We further demonstrate the role of the electron transport layer in affecting the initial concn. of defects close to the selective contacts, highlighting how charge sepn. at the perovskite/TiO2 interface may further change the defect distribution. We believe that this work, identifying the mobile species in perovskite solar cells, their migration across the perovskite material, and their effect on the operational mechanism of the device, may pave the way for the development of new materials and solar cell architectures with improved and stabilized efficiencies. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2MXpt1Sltb4%253D&md5= 147424f62f1c428388260b31bad958ae 67. 67 Svanstrom, S. Degradation Mechanism of Silver Metal Deposited on Lead Halide Perovskites. ACS Appl. Mater. Interfaces 2020, 12, 7212- 7221, DOI: 10.1021/acsami.9b20315 [ACS Full Text ACS Full Text], [CAS], Google Scholar 67 Degradation Mechanism of Silver Metal Deposited on Lead Halide Perovskites Svanstrom Sebastian; Rensmo Hakan; Jacobsson T Jesper; Boschloo Gerrit; Johansson Erik M J; Cappel Ute B ACS applied materials & interfaces (2020), 12 (6), 7212-7221 ISSN:. Lead halide perovskite solar cells have significantly increased in both efficiency and stability over the last decade. An important aspect of their long-term stability is the reaction between the perovskite and other materials in the solar cell. This includes the contact materials and their degradation if they can potentially come into contact through, e.g., pinholes or material diffusion and migration. Here, we explore the interactions of silver contacts with lead halide perovskites of different compositions by using a model system where thermally evaporated silver was deposited directly on the surface of the perovskites. Using X-ray photoelectron spectroscopy with support from scanning electron microscopy, X-ray diffraction, and UV-visible absorption spectroscopy, we studied the film formation and degradation of silver on perovskites with different compositions. The deposited silver does not form a continuous silver film but instead tends to form particles on a bare perovskite surface. These particles are initially metallic in character but degrade into AgI and AgBr over time. The degradation and migration appear unaffected by the replacement of methylammonium with cesium but are significantly slowed down by the complete replacement of iodide with bromide. The direct contact between silver and the perovskite also significantly accelerates the degradation of the perovskite, with a significant loss of organic cations and the possible formation of PbO, and, at the same time, changed the surface morphology of the iodide-rich perovskite interface. Our results further indicate that an important degradation pathway occurred through gas-phase perovskite degradation products. This highlights the importance of control over the interface materials and the use of completely hermetical barrier layers for the long-term stability and therefore the commercial viability of silver electrodes. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A280%3ADC%252BB38%252FitFCmuw%253D%253D&md5= c8e316ffb621703560a2e7664eeabe2c 68. 68 Li, G.-R.; Gao, X.-P. Low-Cost Counter-Electrode Materials for Dye-Sensitized and Perovskite Solar Cells. Adv. Mater. 2020, 32, 1806478, DOI: 10.1002/adma.201806478 [Crossref], [CAS], Google Scholar 68 Low-Cost Counter-Electrode Materials for Dye-Sensitized and Perovskite Solar Cells Li, Guo-Ran; Gao, Xue-Ping Advanced Materials (Weinheim, Germany) (2020), 32 (3), 1806478 CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA) A review. It is un-doubtable that the use of solar energy will continue to increase. Solar cells that convert solar energy directly to electricity are one of the most convenient and important photoelec. conversion devices. Though silicon-based solar cells and thin-film solar cells have been commercialized, developing low-cost and highly efficient solar cells to meet future needs is still a long-term challenge. Some emerging solar-cell types, such as dye-sensitized and perovskite, are approaching acceptable performance levels, but their costs remain too high. To obtain a higher performance-price ratio, it is necessary to find new low-cost counter materials to replace conventional precious metal electrodes (Pt, Au, and Ag) in these emerging solar cells. In recent years, the no. of counter-electrode materials available, and their scope for further improvement, has expanded for dye-sensitized and perovskite solar cells. Generally regular patterns in the intrinsic features and structural design of counter materials for emerging solar cells, in particular from an electrochem. perspective and their effects on cost and efficiency, are explored. It is hoped that this recapitulative anal. will help to make clear what has been achieved and what still remains for the development of cost-effective counter-electrode materials in emerging solar cells. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC1MXhtVejtb%252FF&md5= 02958aaaf8d9397fd1c86fd26c954b31 69. 69 Zhang, Y.; Ng, S.-W.; Lu, X.; Zheng, Z. Solution-Processed Transparent Electrodes for Emerging Thin-Film Solar Cells. Chem. Rev. 2020, 120, 2049- 2122, DOI: 10.1021/acs.chemrev.9b00483 [ACS Full Text ACS Full Text], [CAS], Google Scholar 69 Solution-Processed Transparent Electrodes for Emerging Thin-Film Solar Cells Zhang, Yaokang; Ng, Sze-Wing; Lu, Xi; Zheng, Zijian Chemical Reviews (Washington, DC, United States) (2020), 120 (4), 2049-2122CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society) A review. Soln.-processed solar cells are appealing because of the low manufg. cost, the good compatibility with flexible substrates, and the ease of large-scale fabrication. Whereas soln.-processable active materials have been widely adopted for the fabrication of org., dye-sensitized, and perovskite solar cells, vacuum-deposited transparent conducting oxides (TCOs) such as indium tin oxide, fluorine-doped tin oxide, and aluminum-doped tin oxide are still the most frequently used transparent electrodes (TEs) for solar cells. These TCOs not only significantly increase the manufg. cost of the device, but also are too brittle for future flexible and wearable applications. Therefore, developing soln.-processed TEs for solar cells is of great interest. This paper provides a detailed discussion on the recent development of soln.-processed TEs, including the chem. synthesis of the electrode materials, the soln.-based technologies for the electrode fabrication, the optical and elec. properties of the soln.-processed TEs, and their applications on solar cells. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BB3cXht1CqsLc%253D&md5= d8f4cc9fdae2ce98782e7fca700cb8f5 70. 70 Zhang, J. The Role of 3D Molecular Structural Control in New Hole Transport Materials Outperforming Spiro-OMeTAD in Perovskite Solar Cells. Adv. Energy Mater. 2016, 6, 1601062, DOI: 10.1002/ aenm.201601062 [Crossref], Google Scholar There is no corresponding record for this reference. 71. 71 Tan, H. Efficient and stable solution-processed planar perovskite solar cells via contact passivation. Science 2017, 355, 722- 726, DOI: 10.1126/science.aai9081 [Crossref], [PubMed], [CAS], Google Scholar 71 Efficient and stable solution-processed planar perovskite solar cells via contact passivation Tan, Hairen; Jain, Ankit; Voznyy, Oleksandr; Lan, Xinzheng; Garcia de Arquer, F. Pelayo; Fan, James Z.; Quintero-Bermudez, Rafael; Yuan, Mingjian; Zhang, Bo; Zhao, Yicheng; Fan, Fengjia; Li, Peicheng; Quan, Li Na; Zhao, Yongbiao; Lu, Zheng-Hong; Yang, Zhenyu; Hoogland, Sjoerd; Sargent, Edward H. Science (Washington, DC, United States) (2017), 355 (6326), 722-726CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science) Planar perovskite solar cells (PSCs) made entirely via soln. processing at low temps. (<150degC) offer promise for simple manufg., compatibility with flexible substrates, and perovskite-based tandem devices. However, these PSCs require an electron-selective layer that performs well with similar processing. We report a contact-passivation strategy using chlorine-capped TiO2 colloidal nanocrystal film that mitigates interfacial recombination and improves interface binding in low-temp. planar solar cells. We fabricated solar cells with certified efficiencies of 20.1 and 19.5% for active areas of 0.049 and 1.1 square centimeters, resp., achieved via low-temp. soln. processing. Solar cells with efficiency greater than 20% retained 90% (97% after dark recovery) of their initial performance after 500 h of continuous room-temp. operation at their max. power point under 1-sun illumination (where 1 sun is defined as the std. illumination at AM1.5, or 1 kW/square meter). >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2sXis1yjtbo%253D&md5= c902ae179ca74ae26c435fddaf61ed40 72. 72 Schmidt, T. M.; Larsen-Olsen, T. T.; Carle, J. E.; Angmo, D.; Krebs, F. C. Upscaling of Perovskite Solar Cells: Fully Ambient Roll Processing of Flexible Perovskite Solar Cells with Printed Back Electrodes. Adv. Energy Mater. 2015, 5, 1500569, DOI: 10.1002/aenm.201500569 [Crossref], Google Scholar There is no corresponding record for this reference. 73. 73 Sander, R. Compilation of Henry's law constants (version 4.0) for water as solvent. Atmos. Chem. Phys. 2015, 15, 4399- 4981, DOI: 10.5194/acp-15-4399-2015 [Crossref], [CAS], Google Scholar 73 Compilation of Henry's law constants (version 4.0) for water as solvent Sander, R. Atmospheric Chemistry and Physics (2015), 15 (8), 4399-4981CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications) Many atm. chems. occur in the gas phase as well as in liq. cloud droplets and aerosol particles. Therefore, it is necessary to understand the distribution between the phases. According to Henry's law, the equil. ratio between the abundances in the gas phase and in the aq. phase is const. for a dil. soln. Henry's law consts. of trace gases of potential importance in environmental chem. have been collected and converted into a uniform format. The compilation contains 17350 values of Henry's law consts. for 4632 species, collected from 689 refs. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS&resolution= options&coi=1%3ACAS%3A528%3ADC%252BC2MXotFyktrc%253D&md5= c06fd66b33b6dae9e50f0e9c1e3e60cb Cited By --------------------------------------------------------------------- This article has not yet been cited by other publications. * Figures * References * Support Info * Abstract [sc1c03565_] High Resolution Image Download MS PowerPoint Slide Figure 1 [sc1c03565_] Figure 1. SEM images of the (a-c) NiFeMo-NF and (d) NiFeMo-NP catalysts. The (a) low magnification image reveals the overall catalyst electrode structure with CP fibers coated with NCNTs which in turn are decorated with the trimetallic NiFeMo catalyst. The close-up on a single CP fiber in (b) reveals the dense coating of NCNTs and a NiFeMo catalyst on the CP. The high magnification image in (c) of a single decorated NCNT on a NiFeMo-NF OER electrode reveals that the NCNT is densely covered with a nanoflake-structured NiFeMo catalyst. (d) The NiFeMo catalyst on the HER electrode has been subjected to a reduction process leading to a structural change from nanoflakes to nanoparticles, NiFeMo-NP. High Resolution Image Download MS PowerPoint Slide Figure 2 [sc1c03565_] Figure 2. Electrochemical measurements showing the performance of the NiFeMo-NF and NiFeMo-NP catalyst electrodes for the (a) HER and the (b) OER. (c) Electrochemical measurement of the full water-splitting reaction catalyzed by NiFeMo-NF as the anode and NiFeMo-NP as the cathode. (d) Results from Faradaic efficiency measurements of each catalyst. The triangles correspond to H[2] and the squares to O[2]. The solid lines show the theoretical amount of produced gases at 100% efficiencies. The electrolyte used in all experiments was 1.0 M KOH. High Resolution Image Download MS PowerPoint Slide Figure 3 [sc1c03565_] Figure 3. (a) Schematic of the perovskite solar cell structure. (b) J-V characteristics of the champion cell under AM1.5 illumination. The device features a large open-circuit voltage of 1.09 V and a high solar-to-electric power conversion efficiency of 19.4%. Additional performance metrics are presented in the inset. High Resolution Image Download MS PowerPoint Slide Figure 4 [sc1c03565_] Figure 4. (a) Load line analysis of a solar-driven water-splitting device, as derived from measured J-V data of the PSC (Figure 3b) and the NiFeMo-NF|NiFeMo-NP catalyst-pair electrodes (Figure 2c), with the A[CAT]/A[PSC] ratio increasing from 1 to 10, in steps of 1, as indicated by the arrow. The upper-right inset highlights the operation points, found at the intersections between the catalyst and PSC data, in the region between 1.5-1.8 V. (b) Schematic figure of the water-splitting device with the catalyst electrodes powered by two-series connected PSCs. (c) Calculated I[OP], normalized to the total PSC area (A[PSC]), and STH for various configurations of the solar-driven water-splitting device. The configuration of our tested device, using a two-series connected PSC paired with NiFeMo-NF|NiFeMo-NP catalyst electrodes of A[CAT]/A[PSC] = 8.5, is indicated with an open X. (d) Measured I[OP]/A[PSC] and STH during the 10 h long-term operation for our solar-driven water-splitting device under continuous AM1.5 illumination. The inset in (d) shows the same data on a linear time scale. High Resolution Image Download MS PowerPoint Slide * References ARTICLE SECTIONS Jump To ----------------------------------------------------------------- This article references 73 other publications. 1. 1 World Population Prospects 2019, Rev. 1, 2019. United Nations Department of Economic and Social Affairs. https:// population.un.org/wpp/Publications/Files/ WPP2019_Highlights.pdf accessed October 2021). Google Scholar There is no corresponding record for this reference. 2. 2 World Energy Outlook 2019, 2019. International Energy Agency. https://www.iea.org/reports/world-energy-outlook-2019 (acessed 2021-08-13). Google Scholar There is no corresponding record for this reference. 3. 3 Li, R. Latest progress in hydrogen production from solar water splitting via photocatalysis, photoelectrochemical, and photovoltaic-photoelectrochemical solutions. Chinese Journal of Catalysis. 2017, 38, 5- 12, DOI: 10.1016/S1872-2067(16) 62552-4 [Crossref], [CAS], Google Scholar 3 Latest progress in hydrogen production from solar water splitting via photocatalysis, photoelectrochemical, and photovoltaic-photoelectrochemical solutions Li, Rengui Chinese Journal of Catalysis (2017), 38 (1), 5-12CODEN: CJCHCI ISSN:. (Science Press) A review. Hydrogen prodn. via solar water splitting is regarded as one of the most promising ways to utilize solar energy and has attracted more and more attention. Great progress has been made on photocatalytic water splitting for hydrogen prodn. in the past few years. This review summarizes the very recent progress (mainly in the last 2-3 years) on three major types of solar hydrogen prodn. systems: particulate photocatalysis (PC) systems, photoelectrochem. (PEC) systems, and photovoltaic-photoelectrochem. (PV-PEC) hybrid systems. The solar-to-hydrogen (STH) conversion efficiency of PC systems has recently exceeded 1.0% using a SrTiO3:La,Rh/Au/BiVO4:Mo photocatalyst, 2.5% for PEC water splitting on a tantalum nitride photoanode, and reached 22.4% for PV-PEC water splitting using a multi-junction GaInP/GaAs/ Ge cell and Ni electrode hybrid system. The advantages and disadvantages of these systems for hydrogen prodn. via solar water splitting, esp. for their potential demonstration and application in the future, are briefly described and discussed. Finally, the challenges and opportunities for solar water splitting solns. are also forecasted. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2sXktlGrsbg%253D&md5= 75a8111ec9b2f13851d7bc6741c31dad 4. 4 Chu, S.; Cui, Y.; Liu, N. The path towards sustainable energy . Nat. Mater. 2017, 16, 16- 22, DOI: 10.1038/nmat4834 [Crossref], Google Scholar There is no corresponding record for this reference. 5. 5 Dincer, I.; Acar, C. Review and evaluation of hydrogen production methods for better sustainability. Int. J. Hydrogen Energy 2015, 40, 11094- 11111, DOI: 10.1016/ j.ijhydene.2014.12.035 [Crossref], [CAS], Google Scholar 5 Review and evaluation of hydrogen production methods for better sustainability Dincer, Ibrahim; Acar, Canan International Journal of Hydrogen Energy (2015), 40 (34), 11094-11111CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.) A review. This paper examines various potential methods of hydrogen prodn. using renewable and nonrenewable sources and comparatively assesses them for environmental impact, cost, energy efficiency and exergy efficiency. The social cost of carbon concept is also included to present the relations between environmental impacts and economic factors. Some of the potential primary energy sources considered in this study are: elec., thermal, biochem., photonic, electro-thermal, photoelec., and photo-biochem. When used as the primary energy source, photonic energy based hydrogen prodn. (e.g., photocatalysis, photoelectrochem. method, and artificial photosynthesis) is more environmentally benign than the other selected methods in terms of emissions. Thermochem. water splitting and hybrid thermochem. cycles (e.g. Cu-Cl, S-I, and Mg-Cl) also provide environmentally attractive results. Both photoelectrochem. method and PV electrolysis are least attractive when prodn. costs and efficiencies are considered. Therefore, increasing both energy and exergy efficiencies and decreasing the costs of hydrogen prodn. from solar based hydrogen prodn. have a potential to bring them forefront as potential options. The energy and exergy efficiency comparisons indicate the advantages of fossil fuel reforming and biomass gasification over other methods. Overall rankings show that hybrid thermochem. cycles are primarily promising candidates to produce hydrogen in an environmentally benign and cost-effective way. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2MXitVelug%253D%253D&md5= ffd5713d977bf28c318963c8f376a29f 6. 6 Shaner, M. R.; Atwater, H. A.; Lewis, N. S.; McFarland, E. W. A comparative technoeconomic analysis of renewable hydrogen production using solar energy. Energy Environ. Sci. 2016, 9, 2354- 2371, DOI: 10.1039/C5EE02573G [Crossref], [CAS], Google Scholar 6 A comparative technoeconomic analysis of renewable hydrogen production using solar energy Shaner, Matthew R.; Atwater, Harry A.; Lewis, Nathan S.; McFarland, Eric W. Energy & Environmental Science (2016), 9 (7), 2354-2371CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry) A technoeconomic anal. of photoelectrochem. (PEC) and photovoltaic-electrolytic (PV-E) solar-hydrogen prodn. of 10 000 kg H2 day-1 (3.65 kilotons per yr) was performed to assess the economics of each technol., and to provide a basis for comparison between these technologies as well as within the broader energy landscape. Two PEC systems, differentiated primarily by the extent of solar concn. (unconcd. and 10x concd.) and two PV-E systems, differentiated by the degree of grid connectivity (unconnected and grid supplemented), were analyzed. In each case, a base-case system that used established designs and materials was compared to prospective systems that might be envisioned and developed in the future with the goal of achieving substantially lower overall system costs. With identical overall plant efficiencies of 9.8%, the unconcd. PEC and non-grid connected PV-E system base-case capital expenses for the rated capacity of 3.65 kilotons H2 per yr were $205 MM ($293 per m2 of solar collection area (mS-2), $14.7 WH2,P-1) and $260 MM ($371 mS-2, $18.8 WH2,P-1), resp. The untaxed, plant-gate levelized costs for the hydrogen product (LCH) were $11.4 kg-1 and $12.1 kg-1 for the base-case PEC and PV-E systems, resp. The 10x concd. PEC base-case system capital cost was $160 MM ($428 mS-2, $11.5 WH2,P-1) and for an efficiency of 20% the LCH was $9.2 kg-1. Likewise, the grid supplemented base-case PV-E system capital cost was $66 MM ($441 mS-2, $11.5 WH2,P-1), and with solar-to-hydrogen and grid electrolysis system efficiencies of 9.8% and 61%, resp., the LCH was $6.1 kg-1. As a benchmark, a proton-exchange membrane (PEM) based grid-connected electrolysis system was analyzed. Assuming a system efficiency of 61% and a grid electricity cost of $0.07 kWh-1, the LCH was $5.5 kg-1. A sensitivity anal. indicated that, relative to the base-case, increases in the system efficiency could effect the greatest cost redns. for all systems, due to the areal dependencies of many of the components. The balance-of-systems (BoS) costs were the largest factor in differentiating the PEC and PV-E systems. No single or combination of tech. advancements based on currently demonstrated technol. can provide sufficient cost redns. to allow solar hydrogen to directly compete on a levelized cost basis with hydrogen produced from fossil energy. Specifically, a cost of CO2 greater than ~$800 (ton CO2)-1 was estd. to be necessary for base-case PEC hydrogen to reach price parity with hydrogen derived from steam reforming of methane priced at $12 GJ-1 ($1.39 (kg H2)-1). A comparison with low CO2 and CO2-neutral energy sources indicated that base-case PEC hydrogen is not currently cost-competitive with electrolysis using electricity supplied by nuclear power or from fossil-fuels in conjunction with carbon capture and storage. Solar electricity prodn. and storage using either batteries or PEC hydrogen technologies are currently an order of magnitude greater in cost than electricity prices with no clear advantage to either battery or hydrogen storage as of yet. Significant advances in PEC technol. performance and system cost redns. are necessary to enable cost-effective PEC-derived solar hydrogen for use in scalable grid-storage applications as well as for use as a chem. feedstock precursor to CO2-neutral high energy-d. transportation fuels. Hence such applications are an opportunity for foundational research to contribute to the development of disruptive approaches to solar fuels generation systems that can offer higher performance at much lower cost than is provided by current embodiments of solar fuels generators. Efforts to directly reduce CO2 photoelectrochem. or electrochem. could potentially produce products with higher value than hydrogen, but many, as yet unmet, challenges include catalytic efficiency and selectivity, and CO2 mass transport rates and feedstock cost. Major breakthroughs are required to obtain viable economic costs for solar hydrogen prodn., but the barriers to achieve cost-competitiveness with existing large-scale thermochem. processes for CO2 redn. are even greater. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC28XovFWisb0%253D&md5= 9e19ebf3791f7b67b893bbdeb24ad946 7. 7 Jiang, C.; Moniz, S. J. A.; Wang, A.; Zhang, T.; Tang, J. Photoelectrochemical devices for solar water splitting - materials and challenges. Chem. Soc. Rev. 2017, 46, 4645- 4660, DOI: 10.1039/C6CS00306K [Crossref], [PubMed], [CAS], Google Scholar 7 Photoelectrochemical devices for solar water splitting - materials and challenges Jiang, Chaoran; Moniz, Savio J. A.; Wang, Aiqin; Zhang, Tao; Tang, Junwang Chemical Society Reviews (2017), 46 (15), 4645-4660CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry) A review. It is widely accepted within the community that to achieve a sustainable society with an energy mix primarily based on solar energy we need an efficient strategy to convert and store sunlight into chem. fuels. A photoelectrochem. (PEC) device would therefore play a key role in offering the possibility of carbon-neutral solar fuel prodn. through artificial photosynthesis. The past five years have seen a surge in the development of promising semiconductor materials. In addn., low-cost earth-abundant co-catalysts are ubiquitous in their employment in water splitting cells due to the sluggish kinetics of the oxygen evolution reaction (OER). This review commences with a fundamental understanding of semiconductor properties and charge transfer processes in a PEC device. We then describe various configurations of PEC devices, including single light-absorber cells and multi light-absorber devices (PEC, PV-PEC and PV/electrolyzer tandem cell). Recent progress on both photoelectrode materials (light absorbers) and electrocatalysts is summarized, and important factors which dominate photoelectrode performance, including light absorption, charge sepn. and transport, surface chem. reaction rate and the stability of the photoanode, are discussed. Controlling semiconductor properties is the primary concern in developing materials for solar water splitting. Accordingly, strategies to address the challenges for materials development in this area, such as the adoption of smart architectures, innovative device configuration design, co-catalyst loading, and surface protection layer deposition, are outlined throughout the text, to deliver a highly efficient and stable PEC device for water splitting. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtVGksb3E& md5=49d52d74c034fa6d8303114f78da958a 8. 8 Nikolaidis, P.; Poullikkas, A. A comparative overview of hydrogen production processes. Renewable Sustainable Energy Rev. 2017, 67, 597- 611, DOI: 10.1016/j.rser.2016.09.044 [Crossref], [CAS], Google Scholar 8 A comparative overview of hydrogen production processes Nikolaidis, Pavlos; Poullikkas, Andreas Renewable & Sustainable Energy Reviews (2017), 67 (), 597-611 CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.) Climate change and fossil fuel depletion are the main reasons leading to hydrogen technol. There are many processes for hydrogen prodn. from both conventional and alternative energy resources such as natural gas, coal, nuclear, biomass, solar and wind. In this work, a comparative overview of the major hydrogen prodn. methods is carried out. The process descriptions along with the tech. and economic aspects of 14 different prodn. methods are discussed. An overall comparison is carried out, and the results regarding both the conventional and renewable methods are presented. The thermochem. pyrolysis and gasification are economically viable approaches providing the highest potential to become competitive on a large scale in the near future while conventional methods retain their dominant role in H2 prodn. with costs in the range of 1.34-2.27 $/kg. Biol. methods appear to be a promising pathway but further research studies are needed to improve their prodn. rates, while the low conversion efficiencies in combination with the high investment costs are the key restrictions for water-splitting technologies to compete with conventional methods. However, further development of these technologies along with significant innovations concerning H2 storage, transportation and utilization, implies the decrease of the national dependence on fossil fuel imports and green hydrogen will dominate over the traditional energy resources. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsFarurjL& md5=6cf7ca4fd9c0a23b13ef53d2951ef96c 9. 9 Ball, M.; Weeda, M. The hydrogen economy - Vision or reality? . Int. J. Hydrogen Energy 2015, 40, 7903- 7919, DOI: 10.1016 /j.ijhydene.2015.04.032 [Crossref], [CAS], Google Scholar 9 The hydrogen economy - Vision or reality?1This paper is also published as Chapter 11 'The hydrogen economy - vision or reality?' in Compendium of Hydrogen Energy Volume 4: Hydrogen Use, Safety and the Hydrogen Economy, Edited by Michael Ball, Angelo Basile and T. Nejat Veziroglu, published by Elsevier in 2015, ISBN: 978-1-78242-364-5. For further details see: http://www.elsevier.com/books/compendium-of-hydrogen-energy/ ball/978-1-78242-364-5. Ball, Michael; Weeda, Marcel International Journal of Hydrogen Energy (2015), 40 (25), 7903-7919CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.) When looking at future energy systems, hydrogen offers a range of benefits as a clean energy carrier, which are receiving great attention as policy priorities. This is first and foremost as an alternative fuel in the transport sector. Car makers have recently started the market introduction of fuel cell elec. vehicles and are currently entering a pre-com. phase, as they are progressing from prototype vehicles for demonstration to producing small vols. At the same time, market development initiatives aiming at implementing hydrogen refuelling station networks are spreading in Europe, Asia, and the USA. But also in recent years, hydrogen electrolysis has gained considerable attention as a potential flexibility option to help facilitate the large-scale integration of intermittent renewable energies. Given the sustained interest in and controversial discussions on the prospects of hydrogen, this paper aims to provide a comprehensive coverage of the most relevant aspects related to the wider use of hydrogen in the energy system, including the most recent developments and insights. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2MXntFKhs78%253D&md5= 9e90e48a27f79d9b4a7a4e1a761fe4f1 10. 10 Dutta, S. A review on production, storage of hydrogen and its utilization as an energy resource. J. Ind. Eng. Chem. 2014, 20, 1148- 1156, DOI: 10.1016/j.jiec.2013.07.037 [Crossref], [CAS], Google Scholar 10 A review on production, storage of hydrogen and its utilization as an energy resource Dutta, Suman Journal of Industrial and Engineering Chemistry (Amsterdam, Netherlands) (2014), 20 (4), 1148-1156CODEN: JIECFI; ISSN: 1226-086X. (Elsevier B.V.) A review. Energy price is rising due to rapid depletion of fossil fuels. Development of renewable and non-polluting energy resources is necessary for reducing pollution level caused by those conventional fuels. Researchers have recognized hydrogen (H2) as such an energy source. Hydrogen is a potential non-carbon based energy resource, which can replace fossil fuels. Hydrogen is considered as the alternative fuel as it could be generated from clean and green sources. Despite many advantages, storage of hydrogen is a serious problem. Due to high inflammability, adequate safety measures should be taken during the prodn., storage, and use of H2 fuel. This review article elucidates prodn. methods and storage of hydrogen. Besides this safety related to H2 handling in refilling station, and automobiles has also been discussed. Study shows that safety program and awareness could be fruitful for increasing the acceptance of hydrogen as fuel. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtlansrjI& md5=8b26df1b96cc96f7803331d1957f1dba 11. 11 McCrory, C. C. Benchmarking hydrogen evolving reaction and oxygen evolving reaction electrocatalysts for solar water splitting devices. J. Am. Chem. Soc. 2015, 137, 4347- 4357, DOI: 10.1021/ja510442p [ACS Full Text ACS Full Text], [CAS], Google Scholar 11 Benchmarking Hydrogen Evolving Reaction and Oxygen Evolving Reaction Electrocatalysts for Solar Water Splitting Devices McCrory, Charles C. L.; Jung, Suho; Ferrer, Ivonne M.; Chatman, Shawn M.; Peters, Jonas C.; Jaramillo, Thomas F. Journal of the American Chemical Society (2015), 137 (13), 4347-4357CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society) Objective comparisons of electrocatalyst activity and stability using std. methods under identical conditions are necessary to evaluate the viability of existing electrocatalysts for integration into solar-fuel devices as well as to help inform the development of new catalytic systems. Herein, the authors use a std. protocol as a primary screen for evaluating the activity, short-term (2 h) stability, and electrochem. active surface area (ECSA) of 18 electrocatalysts for the H evolution reaction (HER) and 26 electrocatalysts for the O evolution reaction (OER) under conditions relevant to an integrated solar H2O-splitting device in aq. acidic or alk. soln. The primary figure of merit is the overpotential necessary to achieve a magnitude c.d. of 10 mA cm-2 per geometric area, the approx. c.d. expected for a 10% efficient solar-to-fuels conversion device under 1 sun illumination. The specific activity per ECSA of each material is also reported. Among HER catalysts, several could operate at 10 mA cm-2 with overpotentials <0.1 V in acidic and/or alk. solns. Among OER catalysts in acidic soln., no nonnoble metal based materials showed promising activity and stability, whereas in alk. soln. many OER catalysts performed with similar activity achieving 10 mA cm-2 current densities at overpotentials of ~0.33-0.5 V. Most OER catalysts showed comparable or better specific activity per ECSA when compared to Ir and Ru catalysts in alk. solns., while most HER catalysts showed much lower specific activity than Pt in both acidic and alk. solns. For select catalysts, addnl. secondary screening measurements were conducted including faradaic efficiency and extended stability measurements. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2MXisFyqtrw%253D&md5= 7a45e7400dde5988037aab80ed076b75 12. 12 Kwong, W. L. Cationic Vacancy Defects in Iron Phosphide: A Promising Route toward Efficient and Stable Hydrogen Evolution by Electrochemical Water Splitting. ChemSusChem 2017, 10, 4544- 4551, DOI: 10.1002/cssc.201701565 [Crossref], [PubMed], [CAS], Google Scholar 12 Cationic Vacancy Defects in Iron Phosphide: A Promising Route toward Efficient and Stable Hydrogen Evolution by Electrochemical Water Splitting Kwong, Wai Ling; Gracia-Espino, Eduardo; Lee, Cheng Choo; Sandstroem, Robin; Wagberg, Thomas; Messinger, Johannes ChemSusChem (2017), 10 (22), 4544-4551CODEN: CHEMIZ; ISSN: 1864-5631. (Wiley-VCH Verlag GmbH & Co. KGaA) Engineering the electronic properties of transition metal phosphides has shown great effectiveness in improving their intrinsic catalytic activity for the hydrogen evolution reaction (HER) in water splitting applications. Herein, the creation of Fe vacancies is reported for the first time as an approach to modulate the electronic structure of iron phosphide (FeP). The Fe-vacancies were produced by chem. leaching of Mg that was introduced into FeP as sacrificial dopant. The obtained Fe vacancy-rich FeP nanoparticulate films, which were deposited on Ti foil, show excellent HER activity compared to pristine FeP and Mg-doped FeP, achieving a c.d. of 10 mA cm-2 at overpotentials of 108 mV in 1 M KOH and 65 mV in 0.5 M H2SO4, with a near-100 % Faradaic efficiency. The theor. and exptl. analyses reveal that the improved HER activity originates from the presence of Fe vacancies, which lead to a synergistic modulation of the structural and electronic properties that result in a near-optimal hydrogen adsorption free energy and enhanced proton trapping. The success in catalytic improvement through the introduction of cationic vacancy defects has not only demonstrated the potential of Fe-vacancy-rich FeP as highly efficient, earth abundant HER catalyst, but also opens up an exciting pathway for activating other promising catalysts for electrochem. water splitting. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2sXhslentb%252FM&md5= 5d639d54efddbe243a2404c41e16b49e 13. 13 Zhang, C.; Shi, Y.; Yu, Y.; Du, Y.; Zhang, B. Engineering Sulfur Defects, Atomic Thickness, and Porous Structures into Cobalt Sulfide Nanosheets for Efficient Electrocatalytic Alkaline Hydrogen Evolution. ACS Catal. 2018, 8, 8077- 8083, DOI: 10.1021/acscatal.8b02056 [ACS Full Text ACS Full Text], [CAS], Google Scholar 13 Engineering Sulfur Defects, Atomic Thickness, and Porous Structures into Cobalt Sulfide Nanosheets for Efficient Electrocatalytic Alkaline Hydrogen Evolution Zhang, Chao; Shi, Yanmei; Yu, Yifu; Du, Yonghua; Zhang, Bin ACS Catalysis (2018), 8 (9), 8077-8083CODEN: ACCACS; ISSN: 2155-5435. (American Chemical Society) The development of nonprecious metal-based electrocatalysts with high mass activity and efficient atom utilization for alkali hydrogen evolution reaction (HER) is of great importance for the prepn. of hydrogen resource. The combination of ultrathin and porous structure, esp. with the assistance of vacancy, is expected to be beneficial for achievement of high mass activity, but the development of a facile, robust, and generalized strategy to engineer ultrathin, porous, and vacancy-rich structure into nonlayer structured transition metal-based electrocatalysts is highly challenging. Here, a plasma-induced dry exfoliation method is proposed to prep. nonlayer structured Co3S4 ultrathin porous nanosheets with abundant sulfur vacancies (Co3S4 PNSvac), which show an onset overpotential of only 18 mV and an extremely large mass activity of 1056.6 A g-1 at an overpotential of 200 mV. Exptl. results and theor. calcns. confirm that the efficient alk. HER performance could be attributed to the abundant active sites, good intrinsic activity, and accelerated electron/mass transfer. Addnl., the plasma-assisted conversion method can also be extended to fabricate CoSe2 and NiSe2 ultrathin porous nanosheets with selenium vacancies. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhsVWrsLfE& md5=81bab2e06a434035c69d2fc366e8c450 14. 14 Zhang, T. Engineering oxygen vacancy on NiO nanorod arrays for alkaline hydrogen evolution. Nano Energy 2018, 43, 103- 109, DOI: 10.1016/j.nanoen.2017.11.015 [Crossref], [CAS], Google Scholar 14 Engineering oxygen vacancy on NiO nanorod arrays for alkaline hydrogen evolution Zhang, Tong; Wu, Meng-Ying; Yan, Dong-Yang; Mao, Jing; Liu, Hui; Hu, Wen-Bin; Du, Xi-Wen; Ling, Tao; Qiao, Shi-Zhang Nano Energy (2018), 43 (), 103-109CODEN: NEANCA; ISSN: 2211-2855. (Elsevier Ltd.) Development of low-cost electrocatalysts toward oxygen evolution (OER) and hydrogen evolution reactions (HER) is crucial for large-scale and clean hydrogen prodn. Cost-effective transition metal oxide-based catalysts are superbly active for OER; however, their applications in catalyzing HER remain challenging due to unsatisfactory activity and intrinsically poor electronic cond. Here, we report the synthesis of NiO nanorods (NRs) with abundant oxygen (O) vacancies via a facile cation exchange strategy. Based on the exptl. studies and d. functional theory calcns., we demonstrate that the chem. and electronic property of NiO NRs is successfully optimized through O-vacancy engineering; the O-vacancies on the surface of NiO NRs remarkably enhance their electronic conduction and promote HER reaction kinetics simultaneously. The resulting NiO NRs exhibit excellent alk. HER catalytic activity and durability. Furthermore, these specific designed NiO NRs in situ on carbon fiber paper substrates were directly employed as both HER and OER catalysts for overall water splitting, affording better performance than benchmark Pt and RuO2 catalysts. The successful synthesis of these metal oxides nanomaterials with abundant O-vacancies may pave a new path for rationally fabricating efficient HER/OER bi-functional catalysts. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvVWms7zP& md5=1f8d02f072ce1920bd117a47a0961a99 15. 15 Zhao, Y. Defect-Engineered Ultrathin d-MnO2Nanosheet Arrays as Bifunctional Electrodes for Efficient Overall Water Splitting. Adv. Energy Mater. 2017, 7, 1700005, DOI: 10.1002 /aenm.201700005 [Crossref], Google Scholar There is no corresponding record for this reference. 16. 16 Du, H.; Kong, R. M.; Guo, X.; Qu, F.; Li, J. Recent progress in transition metal phosphides with enhanced electrocatalysis for hydrogen evolution. Nanoscale 2018, 10, 21617- 21624, DOI: 10.1039/C8NR07891B [Crossref], [PubMed], [CAS], Google Scholar 16 Recent progress in transition metal phosphides with enhanced electrocatalysis for hydrogen evolution Du, Huitong; Kong, Rong-Mei; Guo, Xiaoxi; Qu, Fengli; Li, Jinghong Nanoscale (2018), 10 (46), 21617-21624CODEN: NANOHL; ISSN: 2040-3372. (Royal Society of Chemistry) Increasing demand for hydrogen energy has boosted the exploration of inexpensive and effective catalysts. Transition metal phosphides (TMPs) have been proven as excellent catalysts for the hydrogen evolution reaction (HER). Very recently, the search for TMP-based catalysts has being mainly directed at enhanced electrocatalytic performance. Hence, a concluded guideline for enhancing HER activity is highly desired. In this mini review, we briefly summarize the most recent and instructive developments in the design of TMP-based catalysts with enhanced electrocatalysis for hydrogen evolution from compn. and structure engineering strategies. These strategies and perspectives are also meaningful for designing other inexpensive and high-performance catalysts. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitVaqurjK& md5=e4a377dd0d57fb7b989383498694ecb0 17. 17 McKone, J. R.; Sadtler, B. F.; Werlang, C. A.; Lewis, N. S.; Gray, H. B. Ni-Mo Nanopowders for Efficient Electrochemical Hydrogen Evolution. ACS Catal. 2013, 3, 166- 169, DOI: 10.1021/cs300691m [ACS Full Text ACS Full Text], [CAS], Google Scholar 17 Ni-Mo Nanopowders for Efficient Electrochemical Hydrogen Evolution McKone, James R.; Sadtler, Bryce F.; Werlang, Caroline A.; Lewis, Nathan S.; Gray, Harry B. ACS Catalysis (2013), 3 (2), 166-169CODEN: ACCACS; ISSN: 2155-5435. (American Chemical Society) Earth-abundant metals are attractive alternatives to the noble metal composite catalysts that are used in water electrolyzers based on proton-exchange membrane technol. Ni-Mo alloys were previously developed for the hydrogen evolution reaction (HER), but synthesis methods to date were limited to formation of catalyst coatings directly on a substrate. A method is reported for generating unsupported nanopowders of Ni-Mo, which can be suspended in common solvents and cast onto arbitrary substrates. The mass-specific catalytic activity under alk. conditions approaches that of the most active reported non-noble HER catalysts, and the coatings display good stability under alk. conditions. Turnover frequencies are also estd. per surface atom at various overpotentials and concluded that the activity enhancement for Ni-Mo relative to pure Ni is due to a combination of increased surface area and increased fundamental catalytic activity. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhslOls77L& md5=8b191b25429211814582ee2dddec630d 18. 18 Zeng, M.; Li, Y. Recent advances in heterogeneous electrocatalysts for the hydrogen evolution reaction. J. Mater. Chem. A 2015, 3, 14942- 14962, DOI: 10.1039/ C5TA02974K [Crossref], [CAS], Google Scholar 18 Recent advances in heterogeneous electrocatalysts for the hydrogen evolution reaction Zeng, Min; Li, Yanguang Journal of Materials Chemistry A: Materials for Energy and Sustainability (2015), 3 (29), 14942-14962CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry) The hydrogen evolution reaction plays a decisive role in a range of electrochem. and photoelectrochem. devices. It requires efficient and robust electrocatalysts to lower the reaction overpotential and minimize energy consumption. Over the last decade, we have witnessed a rapid rise in new electrocatalysts, particularly those based on non-precious metals. Some of them approach the activity of precious metal benchmarks. Here, we present a comprehensive overview of the recent developments of heterogeneous electrocatalysts for the hydrogen evolution reaction. Detailed discussion is organized from precious metals to non-precious metal compds. including alloys, chalcogenides, carbides, nitrides, borides and phosphides, and finally to metal-free materials. Emphasis is placed on the challenges facing these electrocatalysts and solns. for further improving their performance. We conclude with a perspective on the development of future HER electrocatalysts. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2MXpt1Ogsr0%253D&md5= b3ff2533400b5ecf569482777bc88c6d 19. 19 Vij, V. Nickel-Based Electrocatalysts for Energy-Related Applications: Oxygen Reduction, Oxygen Evolution, and Hydrogen Evolution Reactions. ACS Catal. 2017, 7, 7196- 7225, DOI: 10.1021/acscatal.7b01800 [ACS Full Text ACS Full Text], [CAS], Google Scholar 19 Nickel-Based Electrocatalysts for Energy-Related Applications: Oxygen Reduction, Oxygen Evolution, and Hydrogen Evolution Reactions Vij, Varun; Sultan, Siraj; Harzandi, Ahmad M.; Meena, Abhishek; Tiwari, Jitendra N.; Lee, Wang-Geun; Yoon, Taeseung; Kim, Kwang S. ACS Catalysis (2017), 7 (10), 7196-7225CODEN: ACCACS; ISSN: 2155-5435. (American Chemical Society) A review. The persistently increasing energy consumption and the low abundance of conventional fuels have raised serious concerns all over the world. Thus, the development of technol. for clean-energy prodn. has become the major research priority worldwide. The globalization of advanced energy conversion technologies like rechargeable metal-air batteries, regenerated fuel cells, and H2O-splitting devices was greatly benefitted by the development of apposite catalytic materials that can proficiently carry out the pertinent electrochem. processes like O redn. reaction (ORR), O evolution reaction (OER), H evolution reaction (HER), and H2O hydrolysis. Despite a handful of superbly performing com. catalysts, the high cost and low electrochem. stability of precursors have consistently discouraged their long-term viability. As a promising substitute of conventional Pt-, Pd-, Ir-, Au-, Ag-, and Ru-based catalysts, various transition-metal (TM) ions (for example, Fe, Co, Mo, Ni, V, Cu, etc.) have been exploited to develop advanced electroactive materials to outperform the state-of-the-art catalytic properties. Among these TMs, Ni has emerged as one of the most hopeful constituents due to its exciting electronic properties and anticipated synergistic effect to dramatically alter surface properties of materials to favor electrocatalysis. This review article will broadly confer about recent reports on Ni-based nanoarchitectured materials and their applications toward ORR, OER, HER, and whole H2O splitting. From these applications and properties of Ni derivs., a futuristic outlook of these materials also was presented. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsVeksb7N& md5=c5965edea15dec39a52344e670d6b213 20. 20 Sharifi, T. Hierarchical self-assembled structures based on nitrogen-doped carbon nanotubes as advanced negative electrodes for Li-ion batteries and 3D microbatteries. J. Power Sources 2015, 279, 581- 592, DOI: 10.1016/ j.jpowsour.2015.01.036 [Crossref], [CAS], Google Scholar 20 Hierarchical self-assembled structures based on nitrogen-doped carbon nanotubes as advanced negative electrodes for Li-ion batteries and 3D microbatteries Sharifi, Tiva; Valvo, Mario; Gracia-Espino, Eduardo; Sandstroem, Robin; Edstroem, Kristina; Waagberg, Thomas Journal of Power Sources (2015), 279 (), 581-592CODEN: JPSODZ ; ISSN:0378-7753. (Elsevier B.V.) Hierarchical structures based on C paper and multi-walled N-doped C nanotubes were fabricated and subsequently decorated with hematite nanorods to obtain advanced 3-dimensional architectures for Li-ion battery neg. electrodes. The C paper provides a versatile metal-free 3-dimensional current collector ensuring a good elec. contact of the active materials to its C fiber network. Firstly, the N-doped C nanotubes onto the C paper were studied and a high footprint area capacity of 2.1 mA h cm-2 at 0.1 mA cm-2 was obtained. The Li can be stored in the inter-wall regions of the nanotubes, mediated by the defects formed on their walls by the N atoms. Secondly, the incorporation of hematite nanorods raised the footprint area capacity to 2.25 mA h cm-2 at 0.1 mA cm-2. However, the repeated conversion/ de-conversion of Fe2O3 limited both coulombic and energy efficiencies for these electrodes, which did not perform as well as those including only the N-doped C nanotubes at higher current densities. Thirdly, long-cycling tests showed the robust Li insertion mechanism in these N-doped carbonaceous structures, which yielded an unmatched footprint area capacity enhancement up to 1.95 mA h cm-2 after 60 cycles at 0.3 mA cm-2 and an overall capacity of 204 mA h g-1 referred to the mass of the entire electrode. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2MXksl2ntA%253D%253D&md5= d6a91dc9ceb9827fa7a350729c288b1b 21. 21 Ekspong, J. Stabilizing Active Edge Sites in Semicrystalline Molybdenum Sulfide by Anchorage on Nitrogen-Doped Carbon Nanotubes for Hydrogen Evolution Reaction. Adv. Funct. Mater. 2016, 26, 6766- 6776, DOI: 10.1002/adfm.201601994 [Crossref], [CAS], Google Scholar 21 Stabilizing Active Edge Sites in Semicrystalline Molybdenum Sulfide by Anchorage on Nitrogen-Doped Carbon Nanotubes for Hydrogen Evolution Reaction Ekspong, Joakim; Sharifi, Tiva; Shchukarev, Andrey; Klechikov, Alexey; Wagberg, Thomas; Gracia-Espino, Eduardo Advanced Functional Materials (2016), 26 (37), 6766-6776 CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA) Finding an abundant and cost-effective electrocatalyst for the hydrogen evolution reaction (HER) is crucial for a global prodn. of hydrogen from water electrolysis. This work reports an exceptionally large surface area hybrid catalyst electrode comprising semicryst. molybdenum sulfide (MoS2+x) catalyst attached on a substrate based on nitrogen-doped carbon nanotubes (N-CNTs), which are directly grown on carbon fiber paper (CP). It is shown here that nitrogen-doping of the carbon nanotubes improves the anchoring of MoS2+x catalyst compared to undoped carbon nanotubes and concurrently stabilizes a semicryst. structure of MoS2+x with a high exposure of active sites for HER. The well-connected constituents of the hybrid catalyst are shown to facilitate electron transport and as a result of the good attributes, the MoS2+x/N-CNT/CP electrode exhibits an onset potential of -135 mV for HER in 0.5 M H2SO4, a Tafel slope of 36 mV dec-1, and high stability at a c.d. of -10 mA cm-2. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xht1Wmt77J& md5=4e3c0c0578df64b39a737a2c8f21ecec 22. 22 Zamudio, A. Efficient Anchoring of Silver Nanoparticles on N-Doped Carbon Nanotubes. Small 2006, 2, 346- 350, DOI: 10.1002/smll.200500348 [Crossref], [PubMed], [CAS], Google Scholar 22 Efficient anchoring of silver nanoparticles on N-doped carbon nanotubes Zamudio, Adalberto; Elias, Ana L.; Rodriguez-Manzo, Julio A.; Lopez-Urias, Florentino; Rodriguez-Gattorno, Geonel; Lupo, Fabio; Ruhle, Manfred; Smith, David J.; Terrones, Humberto; Diaz, David; Terrones, Mauricio Small (2006), 2 (3), 346-350CODEN: SMALBC; ISSN:1613-6810. ( Wiley-VCH Verlag GmbH & Co. KGaA) Getting on the tube: A single-step method to attach silver nanoparticles on the surfaces of nitrogen-doped multi-walled carbon nanotubes is described (as depicted in the picture). Ag nanoparticles (2-10 nm diam.) are synthesized by redn. of a Ag salt, and then mixed with the nanotubes in a technique that does not require acid treatment. Similar methods with undoped nanotubes yield less well-coated nanotubes. Interactions with solvent species are believed to play a role in the decoration mechanism. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BD28Xhs1aqs7g%253D&md5= be7d392adc2619d6b70d32d20a36ca42 23. 23 Wang, W.; Luo, J.; Chen, S. Carbon oxidation reactions could misguide the evaluation of carbon black-based oxygen-evolution electrocatalysts. Chem. Commun. (Cambridge, U. K.) 2017, 53, 11556- 11559, DOI: 10.1039/C7CC04611A [Crossref], [PubMed], [CAS], Google Scholar 23 Carbon oxidation reactions could misguide the evaluation of carbon black-based oxygen-evolution electrocatalysts Wang, Wang; Luo, Jin; Chen, Shengli Chemical Communications (Cambridge, United Kingdom) (2017), 53 (84), 11556-11559CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry) A variety of carbon-based materials have been reported as electrocatalysts towards the O evolution reaction. However, C oxidn. during the OER was rarely considered or even neglected in most of the reports. Here, using C black as a model material, we develop a method to est. the contribution of C oxidn. reactions (CORs) to the measured current during the OER test. It is shown that the CORs could result in significant overestimation of the OER activity of C black-based electrocatalysts. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsFylsb3P& md5=91905a983f384c71096aa9c9b191f11b 24. 24 Lu, X.; Yim, W. L.; Suryanto, B. H.; Zhao, C. Electrocatalytic oxygen evolution at surface-oxidized multiwall carbon nanotubes. J. Am. Chem. Soc. 2015, 137, 2901 - 2907, DOI: 10.1021/ja509879r [ACS Full Text ACS Full Text], [CAS], Google Scholar 24 Electrocatalytic Oxygen Evolution at Surface-Oxidized Multiwall Carbon Nanotubes Lu, Xunyu; Yim, Wai-Leung; Suryanto, Bryan H. R.; Zhao, Chuan Journal of the American Chemical Society (2015), 137 (8), 2901-2907CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society) Large-scale storage of renewable energy in the form of hydrogen (H2) fuel via electrolytic water splitting requires the development of water oxidn. catalysts that are efficient and abundant. Carbon-based nanomaterials such as carbon nanotubes have attracted significant applications for use as substrates for anchoring metal-based nanoparticles. It is shown that, upon mild surface oxidn., hydrothermal annealing and electrochem. activation, multiwall carbon nanotubes (MWCNTs) themselves are effective water oxidn. catalysts, which can initiate the oxygen evolution reaction (OER) at overpotentials of 0.3 V in alk. media. Oxygen-contg. functional groups such as ketonic C=O generated on the outer wall of MWCNTs are found to play crucial roles in catalyzing OER by altering the electronic structures of the adjacent carbon atoms and facilitates the adsorption of OER intermediates. The well-preserved microscopic structures and highly conductive inner walls of MWCNTs enable efficient transport of the electrons generated during OER. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2MXitlWmsL4%253D&md5= e9e1a4bc60ad7bbf7e8b3412516b0d70 25. 25 Gong, M. An advanced Ni-Fe layered double hydroxide electrocatalyst for water oxidation. J. Am. Chem. Soc. 2013, 135, 8452- 8455, DOI: 10.1021/ja4027715 [ACS Full Text ACS Full Text], [CAS], Google Scholar 25 An Advanced Ni-Fe Layered Double Hydroxide Electrocatalyst for Water Oxidation Gong, Ming; Li, Yanguang; Wang, Hailiang; Liang, Yongye; Wu, Justin Z.; Zhou, Jigang; Wang, Jian; Regier, Tom; Wei, Fei; Dai, Hongjie Journal of the American Chemical Society (2013), 135 (23), 8452-8455CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society) Highly active, durable, and cost-effective electrocatalysts for H2O oxidn. to evolve O gas hold a key to a range of renewable energy solns., including H2O-splitting and rechargeable metal-air batteries. Here, the authors report the synthesis of ultrathin Ni-Fe layered double hydroxide (NiFe-LDH) nanoplates on mildly oxidized multi-walled C nanotubes (CNTs). Incorporation of Fe into the Ni hydroxide induced the formation of NiFe-LDH. The cryst. NiFe-LDH phase in nanoplate form is highly active for O evolution reaction in alk. solns. For NiFe-LDH grown on a network of CNTs, the resulting NiFe-LDH/CNT complex exhibits higher electrocatalytic activity and stability for O evolution than com. precious metal Ir catalysts. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC3sXot1alu78%253D&md5= 90ff0f80019554e2e5d436a5590f7cf7 26. 26 Song, F.; Hu, X. Exfoliation of layered double hydroxides for enhanced oxygen evolution catalysis. Nat. Commun. 2014, 5, 4477, DOI: 10.1038/ncomms5477 [Crossref], [PubMed], [CAS], Google Scholar 26 Exfoliation of layered double hydroxides for enhanced oxygen evolution catalysis Song, Fang; Hu, Xile Nature Communications (2014), 5 (), 4477CODEN: NCAOBW; ISSN: 2041-1723. (Nature Publishing Group) The oxygen evolution reaction is a key reaction in water splitting. The common approach in the development of oxygen evolution catalysts is to search for catalytic materials with new and optimized chem. compns. and structures. Here we report an orthogonal approach to improve the activity of catalysts without alternating their compns. or structures. Specifically, liq. phase exfoliation is applied to enhance the oxygen evolution activity of layered double hydroxides. The exfoliated single-layer nanosheets exhibit significantly higher oxygen evolution activity than the corresponding bulk layered double hydroxides in alk. conditions. The nanosheets from nickel iron and nickel cobalt layered double hydroxides outperform a com. iridium dioxide catalyst in both activity and stability. The exfoliation creates more active sites and improves the electronic cond. This work demonstrates the promising catalytic activity of single-layered double hydroxides for the oxygen evolution reaction. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2cXitVShs7%252FE&md5= ca5d2d80f1409c80b596494e74520a10 27. 27 Liu, L.; Wu, H.; She, L. Tuning Microstructures of Iron-Nickel Alloy Catalysts for Efficient Oxygen Evolution Reaction. Chem. J. Chin. Univ. 2020, 41, 1083- 1090, DOI: 10.7503/cjcu20190660 [Crossref], Google Scholar There is no corresponding record for this reference. 28. 28 Zhang, B. Homogeneously dispersed, multimetal oxygen-evolving catalysts. Science 2016, 352, 333- 337, DOI: 10.1126/ science.aaf1525 [Crossref], [PubMed], [CAS], Google Scholar 28 Homogeneously dispersed multimetal oxygen-evolving catalysts Zhang, Bo; Zheng, Xueli; Voznyy, Oleksandr; Comin, Riccardo; Bajdich, Michal; Garcia-Melchor, Max; Han, Lili; Xu, Jixian; Liu, Min; Zheng, Lirong; Garcia de Arquer, F. Pelayo; Dinh, Cao Thang; Fan, Fengjia; Yuan, Mingjian; Yassitepe, Emre; Chen, Ning; Regier, Tom; Liu, Pengfei; Li, Yuhang; De Luna, Phil; Janmohamed, Alyf; Xin, Huolin L.; Yang, Huagui; Vojvodic, Aleksandra; Sargent, Edward H. Science (Washington, DC, United States) (2016), 352 (6283), 333-337CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science) Earth-abundant first-row (3d) transition metal-based catalysts were developed for the oxygen-evolution reaction (OER); however, they operate at overpotentials substantially above thermodn. requirements. D. functional theory suggested that non-3d high-valency metals such as tungsten can modulate 3d metal oxides, providing near-optimal adsorption energies for OER intermediates. A room-temp. synthesis is developed to produce gelled oxyhydroxides materials with an atomically homogeneous metal distribution. These gelled FeCoW oxyhydroxides exhibit the lowest overpotential (191 mV) reported at 10 mA per square centimeter in alk. electrolyte. The catalyst shows no evidence of degrdn. after more than 500 h of operation. X-ray absorption and computational studies reveal a synergistic interplay between tungsten, iron, and cobalt in producing a favorable local coordination environment and electronic structure that enhance the energetics for OER. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC28Xlsl2isLk%253D&md5= d2b80a4091e08859b95ca5900015c186 29. 29 Jin, Y. Porous MoO2 Nanosheets as Non-noble Bifunctional Electrocatalysts for Overall Water Splitting. Adv. Mater. 2016, 28, 3785- 3790, DOI: 10.1002/adma.201506314 [Crossref], [PubMed], [CAS], Google Scholar 29 Porous MoO2 Nanosheets as Non-noble Bifunctional Electrocatalysts for Overall Water Splitting Jin, Yanshuo; Wang, Haotian; Li, Junjie; Yue, Xin; Han, Yujie; Shen, Pei Kang; Cui, Yi Advanced Materials (Weinheim, Germany) (2016), 28 (19), 3785-3790CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA) Porous MoO2 nanosheets were directly grown on com. nickel foam without binder by a simple wet-chem. route first and then with an annealing treatment. The porous MoO2 shows much higher activity toward both HER and OER than the compact MoO2, which could be attributed to the higher surface area and more active sites contributed by porous nanostructuring. As an active and stable bifunctional electrocatalyst for overall water splitting, the porous MoO2 needs a cell voltage of only about 1.53 V to achieve c.d. of 10 mA cm-2 and maintains its activity for at least 24 h in a two-electrode configuration and 1 M KOH. The water-splitting device can be powered by an AA battery with a nominal voltage of 1.5 V at room temp. Porous MoO2 is one of the best high-performance bifunctional electrocatalysts for overall water splitting and this work offers an attractive cost-effective catalytic material toward overall water splitting. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC28Xks1ekur8%253D&md5= 7fa8404fd632e9db05e4b2411c02924a 30. 30 Krstajic, N. V. Non-noble metal composite cathodes for hydrogen evolution. Part I: The Ni-MoOx coatings electrodeposited from Watt's type bath containing MoO3 powder particles. Int. J. Hydrogen Energy 2011, 36, 6441- 6449, DOI: 10.1016/j.ijhydene.2011.02.105 [Crossref], [CAS], Google Scholar 30 Non-noble metal composite cathodes for hydrogen evolution. The Ni-MoOx coatings electrodeposited from Watt's type bath containing MoO3 powder particles Krstajic, N. V.; Gajic-Krstajic, Lj.; Lacnjevac, U.; Jovic, B. M.; Mora, S.; Jovic, V. D. International Journal of Hydrogen Energy (2011), 36 (11), 6441-6449CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.) In this work, the Ni-MoOx coatings have been prepd. and characterized in view of their possible application as electrocatalysts for hydrogen evolution reaction (HER) in alk. soln. The procedure of deposition of Ni-MoOx coatings from the Watt's type bath contg. MoO3 powder particles onto Ni mesh, under the conditions of simulated industrial deposition conditions for com. cathodes, has been presented. The morphol. of the obtained coatings was investigated by SEM, the compn. by EDS and the phase compn. by XRD techniques. The polarization characteristics for hydrogen evolution on the obtained Ni-MoOx coatings were investigated in the 32 wt. % NaOH at 90 degC and compared with the one recorded for the com. De Nora's coating (DN). It was shown that the best Ni-MoOx coating exhibits almost identical polarization characteristics as the com. one. By the cross section and XRD anal. of deposited samples it was confirmed that MoO3 powder particles were not occluded by the Ni deposit and that molybdenum species were deposited from the molybdate ions formed by dissoln. of MoO3, following the mechanism of induced co-deposition. The reaction mechanism for MoO3 phase deposition has also been proposed. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC3MXlslKrsrw%253D&md5= fd7513b6a7dd6ef5daee4e08f885a5c8 31. 31 Luo, Z. Mesoporous MoO3-x Material as an Efficient Electrocatalyst for Hydrogen Evolution Reactions. Adv. Energy Mater. 2016, 6, 1600528, DOI: 10.1002/aenm.201600528 [Crossref], Google Scholar There is no corresponding record for this reference. 32. 32 Jin, Y.; Shen, P. K. Nanoflower-like metallic conductive MoO2 as a high-performance non-precious metal electrocatalyst for the hydrogen evolution reaction. J. Mater. Chem. A 2015, 3, 20080- 20085, DOI: 10.1039/C5TA06018D [Crossref], [CAS], Google Scholar 32 Nanoflower-like metallic conductive MoO2 as a high-performance non-precious metal electrocatalyst for the hydrogen evolution reaction Jin, Yanshuo; Shen, Pei Kang Journal of Materials Chemistry A: Materials for Energy and Sustainability (2015), 3 (40), 20080-20085CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry) Searching for nonprecious metal electrocatalysts with high activity and stability for the H evolution reaction (HER) has attracted considerable attention. Herein, the authors report the synthesis of nanoflower-like MoO2 on Ni foam (NFL MoO2/ NF). Remarkably, as a HER electrocatalyst operating in alk. electrolytes, NFL MoO2/NF exhibits high stability and activity. The onset potential of NFL MoO2/NF is almost 0 V vs. the reversible H electrode (RHE) and bubbles can be produced on the surface of NFL MoO2/NF under a static overpotential of only 10 mV, comparable to com. Pt/C. NFL MoO2/NF needs overpotentials of only ~55 and 80 mV to achieve current densities of 10 and 20 mA cm-2, resp. NFL MoO2/NF has superior stability in the long-term electrochem. process and retains 94.3% of its initial c.d. after 25 h. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsVygtrfK& md5=9c0990cce798fdbba474082fa16437a2 33. 33 Tian, J. Self-supported NiMo hollow nanorod array: an efficient 3D bifunctional catalytic electrode for overall water splitting. J. Mater. Chem. A 2015, 3, 20056- 20059, DOI: 10.1039/C5TA04723D [Crossref], [CAS], Google Scholar 33 Self-supported NiMo hollow nanorod array: an efficient 3D bifunctional catalytic electrode for overall water splitting Tian, Jingqi; Cheng, Ningyan; Liu, Qian; Sun, Xuping; He, Yuquan; Asiri, Abdullah M. Journal of Materials Chemistry A: Materials for Energy and Sustainability (2015), 3 (40), 20056-20059CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry) Large-scale industrial application of electrochem. H2O splitting calls for remarkable nonnoble metal electrocatalysts. Herein, the authors report on the synthesis of a NiMo-alloy hollow nanorod array supported on Ti mesh (NiMo HNRs/TiM) using a template-assisted electrodeposition method. The NiMo HNRs/TiM behaves as a durable efficient O evolution anode with 10 mA cm-2 at an overpotential of 310 mV in 1.0 M KOH. Coupled with its superior catalytic performance for H evolution with 10 mA cm-2 at an overpotential of 92 mV, the authors made an alk. electrolyzer using this bifunctional electrode with 10 mA cm-2 at a cell voltage of 1.64 V. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsVSjurzN& md5=aa961cfc94d2497ece482e6a934cef5e 34. 34 Wiggins-Camacho, J. D.; Stevenson, K. J. Effect of Nitrogen Concentration on Capacitance, Density of States, Electronic Conductivity, and Morphology of N-Doped Carbon Nanotube Electrodes. J. Phys. Chem. C 2009, 113, 19082- 19090, DOI: 10.1021/jp907160v [ACS Full Text ACS Full Text], [CAS], Google Scholar 34 Effect of Nitrogen Concentration on Capacitance, Density of States, Electronic Conductivity, and Morphology of N-Doped Carbon Nanotube Electrodes Wiggins-Camacho, Jaclyn D.; Stevenson, Keith J. Journal of Physical Chemistry C (2009), 113 (44), 19082-19090 CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society) Heteroatom doping (e.g., boron and nitrogen) of graphitic carbon lattices affects various physicochem. properties of sp2 carbon materials. The influence of nitrogen doping in carbon nanotubes (N-CNTs) on their electrochem. and elec. properties such as the differential capacitance, d. of states at the Fermi level (D(EF)), bulk cond., and work function is presented. Studies were performed on free-standing N-CNTs electrode mats to understand the intrinsic physicochem. properties of the material without relying on the secondary influence of another conductive support. N-Doping levels ranging from 0 to 7.4 at.% N were examd., and electrochem. impedance spectroscopy (EIS) was used to evaluate the differential capacitance and to est. the effective d. of states, D(EF). XPS and Raman microscopy were used to assess the compositional and structural properties as a function of nitrogen doping. XPS N1s spectra show three principle types of nitrogen coordination (pyridinic, pyrrolic, and quaternary). Raman was used as diagnostic tool for estg. the amt. of disorder by comparing D and G bands. A linear increase in the ratio of integrated D and G band intensities with nitrogen doping indicates that the amt. of disorder and no. of edge plane sites increase. Furthermore, D(EF) also increases with N doping and the amt. of disorder and no. of edge plane sites. UPS (UPS) was used to probe the valence band of N-CNTs in order to est. the work function of the mats. The work function increased linearly from 4.1 to 4.5 eV for increasing N-doping levels. The bulk elec. cond. of the N-CNT electrode mats appears to be junction dominated as shown by the relationship between the bulk cond. and av. N-CNT length within the mats detd. using high-resoln. scanning TEM (STEM). >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXht1CgtrrF& md5=9bd2f88d84422695a5c46fa60b97f379 35. 35 Fabbri, E.; Habereder, A.; Waltar, K.; Kotz, R.; Schmidt, T. J. Developments and perspectives of oxide-based catalysts for the oxygen evolution reaction. Catal. Sci. Technol. 2014, 4, 3800- 3821, DOI: 10.1039/C4CY00669K [Crossref], [CAS], Google Scholar 35 Developments and perspectives of oxide-based catalysts for the oxygen evolution reaction Fabbri, E.; Habereder, A.; Waltar, K.; Kotz, R.; Schmidt, T. J. Catalysis Science & Technology (2014), 4 (11), 3800-3821 CODEN: CSTAGD; ISSN:2044-4753. (Royal Society of Chemistry) A review. The growing need to store large amts. of energy produced from renewable sources has recently directed substantial R&D efforts towards water electrolysis technologies. Although the description of the electrochem. reaction of water electrolysis dates back to the late 18th century, improvements in terms of efficiency and stability are foreseen for a widespread market penetration of water electrolyzers. Particular advances are required for the electrode materials catalyzing the oxygen evolution reaction (OER) at the anode side, which has slow kinetics and thus is one of the major sources of the cell efficiency loss. In recent years, high-level theor. tools and computational studies have led to significant progress in the at.-level understanding of the OER and electrocatalyst behavior. In parallel, several exptl. studies have explored new catalytic materials with advanced properties and kinetics on a tech. relevant level. This contribution summarizes previous and the most recent theor. predictions and exptl. outcomes in the field of oxide-based catalysts for the OER, both operating in acidic and alk. environments. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtFWhs73K& md5=1e03eaf45f961a58eb2c54e86d8c2b93 36. 36 Ekspong, J.; Wagberg, T. Stainless Steel as A Bi-Functional Electrocatalyst-A Top-Down Approach. Materials 2019, 12, 2128 , DOI: 10.3390/ma12132128 [Crossref], [CAS], Google Scholar 36 Stainless steel as a bi-functional electrocatalyst-a top-down approach Ekspong, Joakim; Wagberg, Thomas Materials (2019), 12 (13), 2128CODEN: MATEG9; ISSN:1996-1944. (MDPI AG) For a hydrogen economy to be viable, clean and economical hydrogen prodn. methods are vital. Electrolysis of water is a promising hydrogen prodn. technique with zero emissions, but suffer from relatively high prodn. costs. In order to make electrolysis of water sustainable, abundant, and efficient materials has to replace expensive and scarce noble metals as electrocatalysts in the reaction cells. Herein, we study activated stainless steel as a bi-functional electrocatalyst for the full water splitting reaction by taking advantage of nickel and iron suppressed within the bulk. The final electrocatalyst consists of a stainless steel mesh with a modified surface of layered NiFe nanosheets. By using a top down approach, the nanosheets stay well anchored to the surface and maintain an excellent elec. connection to the bulk structure. At ambient temp., the activated stainless steel electrodes produce 10 mA/cm2 at a cell voltage of 1.78 V and display an onset for water splitting at 1.68 V in 1M KOH, which is close to benchmarking nanosized catalysts. Furthermore, we use a scalable activation method using no externally added electrocatalyst, which could be a practical and cheap alternative to traditionally catalyst-coated electrodes. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BB3cXis1aqt7s%253D&md5= 0195f529ab8e35c5e8b73e72999733a2 37. 37 Gong, M. Nanoscale nickel oxide/nickel heterostructures for active hydrogen evolution electrocatalysis. Nat. Commun. 2014 , 5, 4695, DOI: 10.1038/ncomms5695 [Crossref], [PubMed], [CAS], Google Scholar 37 Nanoscale nickel oxide/nickel heterostructures for active hydrogen evolution electrocatalysis Gong, Ming; Zhou, Wu; Tsai, Mon-Che; Zhou, Jigang; Guan, Mingyun; Lin, Meng-Chang; Zhang, Bo; Hu, Yongfeng; Wang, Di-Yan; Yang, Jiang; Pennycook, Stephen J.; Hwang, Bing-Joe; Dai, Hongjie Nature Communications (2014), 5 (), 4695CODEN: NCAOBW; ISSN: 2041-1723. (Nature Publishing Group) Active, stable and cost-effective electrocatalysts are a key to water splitting for hydrogen prodn. through electrolysis or photoelectrochem. Here we report nanoscale nickel oxide/ nickel heterostructures formed on carbon nanotube sidewalls as highly effective electrocatalysts for hydrogen evolution reaction with activity similar to platinum. Partially reduced nickel interfaced with nickel oxide results from thermal decompn. of nickel hydroxide precursors bonded to carbon nanotube sidewalls. The metal ion-carbon nanotube interactions impede complete redn. and Ostwald ripening of nickel species into the less hydrogen evolution reaction active pure nickel phase. A water electrolyzer that achieves ~20 mA cm-2 at a voltage of 1.5 V, and which may be operated by a single-cell alk. battery, is fabricated using cheap, non-precious metal-based electrocatalysts. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2MXksVChtr8%253D&md5= 39664eecc487dbc1cf7fef21e874ec32 38. 38 Shinagawa, T.; Garcia-Esparza, A. T.; Takanabe, K. Insight on Tafel slopes from a microkinetic analysis of aqueous electrocatalysis for energy conversion. Sci. Rep. 2015, 5, 13801, DOI: 10.1038/srep13801 [Crossref], [PubMed], [CAS], Google Scholar 38 Insight on Tafel slopes from a microkinetic analysis of aqueous electrocatalysis for energy conversion Shinagawa Tatsuya; Garcia-Esparza Angel T; Takanabe Kazuhiro Scientific reports (2015), 5 (), 13801 ISSN:. Microkinetic analyses of aqueous electrochemistry involving gaseous H2 or O2, i.e., hydrogen evolution reaction (HER), hydrogen oxidation reaction (HOR), oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), are revisited. The Tafel slopes used to evaluate the rate determining steps generally assume extreme coverage of the adsorbed species (th[?]0 or [?]1), although, in practice, the slopes are coverage-dependent. We conducted detailed kinetic analyses describing the coverage-dependent Tafel slopes for the aforementioned reactions. Our careful analyses provide a general benchmark for experimentally observed Tafel slopes that can be assigned to specific rate determining steps. The Tafel analysis is a powerful tool for discussing the rate determining steps involved in electrocatalysis, but our study also demonstrated that overly simplified assumptions led to an inaccurate description of the surface electrocatalysis. Additionally, in many studies, Tafel analyses have been performed in conjunction with the Butler-Volmer equation, where its applicability regarding only electron transfer kinetics is often overlooked. Based on the derived kinetic description of the HER/HOR as an example, the limitation of Butler-Volmer expression in electrocatalysis is also discussed in this report. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A280%3ADC%252BC283gsFeluw%253D%253D&md5= ac27784a48ec67e4bea1ac3d6c62a416 39. 39 Ekspong, J.; Gracia-Espino, E.; Wagberg, T. Hydrogen Evolution Reaction Activity of Heterogeneous Materials: A Theoretical Model. J. Phys. Chem. C 2020, 124, 20911- 20921, DOI: 10.1021/acs.jpcc.0c05243 [ACS Full Text ACS Full Text], [CAS], Google Scholar 39 Hydrogen Evolution Reaction Activity of Heterogeneous Materials: A Theoretical Model Ekspong, Joakim; Gracia-Espino, Eduardo; Waagberg, Thomas Journal of Physical Chemistry C (2020), 124 (38), 20911-20921 CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society) In this study, we present a new comprehensive methodol. to quantify the catalytic activity of heterogeneous materials for the hydrogen evolution reaction (HER) using ab initio simulations. The model is composed of two parts. First, the equil. hydrogen coverage is obtained by an iterative evaluation of the hydrogen adsorption free energies (DGH) using d. functional theory calcns. Afterward, the DGH are used in a microkinetic model to provide detailed characterizations of the entire HER considering all three elementary steps, i.e., the discharge, atom + ion, and combination reactions, without any prior assumptions of rate-detg. steps. The microkinetic model takes the equil. and potential-dependent characteristics into account, and thus both exchange current densities and Tafel slopes are evaluated. The model is tested on several systems, from polycryst. metals to heterogeneous molybdenum disulfide (MoS2), and by comparing to exptl. data, we verify that our model accurately predicts their exptl. exchange current densities and Tafel slopes. Finally, we present an extended volcano plot that correlates the elec. current densities of each elementary reaction step to the coverage-dependent DGH. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhs1aqsL7N& md5=b344e1b4b9dc1a270294b4f8238ef72d 40. 40 Suen, N.-T. Electrocatalysis for the oxygen evolution reaction: recent development and future perspectives. Chem. Soc. Rev. 2017, 46, 337- 365, DOI: 10.1039/C6CS00328A [Crossref], [PubMed], [CAS], Google Scholar 40 Electrocatalysis for the oxygen evolution reaction: recent development and future perspectives Suen, Nian-Tzu; Hung, Sung-Fu; Quan, Quan; Zhang, Nan; Xu, Yi-Jun; Chen, Hao Ming Chemical Society Reviews (2017), 46 (2), 337-365CODEN: CSRVBR ; ISSN:0306-0012. (Royal Society of Chemistry) There is still an ongoing effort to search for sustainable, clean and highly efficient energy generation to satisfy the energy needs of modern society. Among various advanced technologies, electrocatalysis for the oxygen evolution reaction (OER) plays a key role and numerous new electrocatalysts have been developed to improve the efficiency of gas evolution. Along the way, enormous effort has been devoted to finding high-performance electrocatalysts, which has also stimulated the invention of new techniques to investigate the properties of materials or the fundamental mechanism of the OER. This accumulated knowledge not only establishes the foundation of the mechanism of the OER, but also points out the important criteria for a good electrocatalyst based on a variety of studies. Even though it may be difficult to include all cases, the aim of this review is to inspect the current progress and offer a comprehensive insight toward the OER. This review begins with examg. the theor. principles of electrode kinetics and some measurement criteria for achieving a fair evaluation among the catalysts. The second part of this review acquaints some materials for performing OER activity, in which the metal oxide materials build the basis of OER mechanism while non-oxide materials exhibit greatly promising performance toward overall water-splitting. Attention of this review is also paid to in situ approaches to electrocatalytic behavior during OER, and this information is crucial and can provide efficient strategies to design perfect electrocatalysts for OER. Finally, the OER mechanism from the perspective of both recent exptl. and theor. investigations is discussed, as well as probable strategies for improving OER performance with regards to future developments. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2sXpslKksQ%253D%253D&md5= 3439b70760b2146baf20bddfa0447207 41. 41 Hall, D. S.; Lockwood, D. J.; Bock, C.; MacDougall, B. R. Nickel hydroxides and related materials: a review of their structures, synthesis and properties. Proc. R. Soc. London, Ser. A 2015, 471, 20140792, DOI: 10.1098/rspa.2014.0792 [Crossref], Google Scholar There is no corresponding record for this reference. 42. 42 Dionigi, F.; Strasser, P. NiFe-Based (Oxy)hydroxide Catalysts for Oxygen Evolution Reaction in Non-Acidic Electrolytes. Adv. Energy Mater. 2016, 6, 1600621, DOI: 10.1002/ aenm.201600621 [Crossref], Google Scholar There is no corresponding record for this reference. 43. 43 Trotochaud, L.; Young, S. L.; Ranney, J. K.; Boettcher, S. W. Nickel-Iron Oxyhydroxide Oxygen-Evolution Electrocatalysts: The Role of Intentional and Incidental Iron Incorporation. J. Am. Chem. Soc. 2014, 136, 6744- 6753, DOI: 10.1021/ja502379c [ACS Full Text ACS Full Text], [CAS], Google Scholar 43 Nickel-Iron Oxyhydroxide Oxygen-Evolution Electrocatalysts: The Role of Intentional and Incidental Iron Incorporation Trotochaud, Lena; Young, Samantha L.; Ranney, James K.; Boettcher, Shannon W. Journal of the American Chemical Society (2014), 136 (18), 6744-6753CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society) Fe plays a crit., but not yet understood, role in enhancing the activity of the Ni-based O evolution reaction (OER) electrocatalysts. The authors report electrochem., in situ elec., photoelectron spectroscopy, and x-ray diffraction measurements on Ni1-xFex(OH)2/Ni1-xFexOOH thin films to study the changes in electronic properties, OER activity, and structure as a result of Fe inclusion. The authors developed a simple method for purifn. of KOH electrolyte that uses pptd. bulk Ni(OH)2 to absorb Fe impurities. Cyclic voltammetry on rigorously Fe-free Ni(OH)2/NiOOH reveals new Ni redox features and no significant OER current until >400 mV overpotential, different from previous reports which were likely affected by Fe impurities. The authors show through controlled crystn. that b-NiOOH is less active for OER than the disordered g-NiOOH starting material and that previous reports of increased activity for b-NiOOH are due to incorporation of Fe-impurities during the crystn. process. Through-film in situ cond. measurements show a >30-fold increase in film cond. with Fe addn., but this change in cond. is not sufficient to explain the obsd. changes in activity. Measurements of activity as a function of film thickness on Au and glassy C substrates are consistent with the hypothesis that Fe exerts a partial-charge-transfer activation effect on Ni, similar to that obsd. for noble-metal electrode surfaces. These results have significant implications for the design and study of Ni1-xFexOOH OER electrocatalysts, which are the fastest measured OER catalysts under basic conditions. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2cXmtlygtLc%253D&md5= 6a26a961800255dfe91df6d95388f64d 44. 44 Costa, J. D. Electrocatalytic Performance and Stability of Nanostructured Fe-Ni Pyrite-Type Diphosphide Catalyst Supported on Carbon Paper. J. Phys. Chem. C 2016, 120, 16537- 16544, DOI: 10.1021/acs.jpcc.6b05783 [ACS Full Text ACS Full Text], Google Scholar There is no corresponding record for this reference. 45. 45 Kojima, A.; Teshima, K.; Shirai, Y.; Miyasaka, T. Organometal halide perovskites as visible-light sensitizers for photovoltaic cells. J. Am. Chem. Soc. 2009, 131, 6050- 6051, DOI: 10.1021/ja809598r [ACS Full Text ACS Full Text], [CAS], Google Scholar 45 Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells Kojima, Akihiro; Teshima, Kenjiro; Shirai, Yasuo; Miyasaka, Tsutomu Journal of the American Chemical Society (2009), 131 (17), 6050-6051CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society) Two organolead halide perovskite nanocrystals, MeNH3PbBr3 and MeNH3PbI3, efficiently sensitize TiO2 for visible-light conversion in photoelectrochem. cells. When self-assembled on mesoporous TiO2 films, the nanocryst. perovskites exhibit strong band-gap absorptions as semiconductors. The MeNH3PbI3-based photocell with spectral sensitivity of up to 800 nm yielded a solar energy conversion efficiency of 3.8%. The MeNH3PbBr3-based cell showed a high photovoltage of 0.96 V with an external quantum conversion efficiency of 65%. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BD1MXksV2iurc%253D&md5= fc3cee6cc3a6955da4fe9e344fdcd3b9 46. 46 Lee, M. M.; Teuscher, J.; Miyasaka, T.; Murakami, T. N.; Snaith, H. J. Efficient hybrid solar cells based on meso-superstructured organometal halide perovskites. Science 2012, 338, 643- 647, DOI: 10.1126/science.1228604 [Crossref], [PubMed], [CAS], Google Scholar 46 Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites Lee, Michael M.; Teuscher, Joel; Miyasaka, Tsutomu; Murakami, Takurou N.; Snaith, Henry J. Science (Washington, DC, United States) (2012), 338 (6107), 643-647CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science) The energy costs assocd. with sepg. tightly bound excitons (photoinduced electron-hole pairs) and extg. free charges from highly disordered low-mobility networks represent fundamental losses for many low-cost photovoltaic technologies. A low-cost, soln.-processable solar cell is reported, based on a highly cryst. perovskite absorber with intense visible to near-IR absorptivity, that has a power conversion efficiency of 10.9% in a single-junction device under simulated full sunlight. This "meso-superstructured solar cell" exhibits exceptionally few fundamental energy losses; it can generate open-circuit photovoltages of more than 1.1 V, despite the relatively narrow absorber band gap of 1.55 eV. The functionality arises from the use of mesoporous alumina as an inert scaffold that structures the absorber and forces electrons to reside in and be transported through the perovskite. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsFygtbrL& md5=fdddb80f46817da2f0d11f6434746226 47. 47 Burschka, J. Sequential deposition as a route to high-performance perovskite-sensitized solar cells. Nature 2013, 499, 316- 319, DOI: 10.1038/nature12340 [Crossref], [PubMed], [CAS], Google Scholar 47 Sequential deposition as a route to high-performance perovskite-sensitized solar cells Burschka, Julian; Pellet, Norman; Moon, Soo-Jin; Humphry-Baker, Robin; Gao, Peng; Nazeeruddin, Mohammad K.; Graetzel, Michael Nature (London, United Kingdom) (2013), 499 (7458), 316-319 CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group) Following pioneering work, soln.-processable org.-inorg. hybrid perovskites-such as CH3NH3PbX3 (X = Cl, Br, I)-have attracted attention as light-harvesting materials for mesoscopic solar cells. So far, the perovskite pigment has been deposited in a single step onto mesoporous metal oxide films using a mixt. of PbX2 and CH3NH3X in a common solvent. However, the uncontrolled pptn. of the perovskite produces large morphol. variations, resulting in a wide spread of photovoltaic performance in the resulting devices, which hampers the prospects for practical applications. Here we describe a sequential deposition method for the formation of the perovskite pigment within the porous metal oxide film. PbI2 is first introduced from soln. into a nanoporous titanium dioxide film and subsequently transformed into the perovskite by exposing it to a soln. of CH3NH3I. We find that the conversion occurs within the nanoporous host as soon as the two components come into contact, permitting much better control over the perovskite morphol. than is possible with the previously employed route. Using this technique for the fabrication of solid-state mesoscopic solar cells greatly increases the reproducibility of their performance and allows us to achieve a power conversion efficiency of approx. 15 per cent (measured under std. AM1.5G test conditions on solar zenith angle, solar light intensity and cell temp.). This two-step method should provide new opportunities for the fabrication of soln.-processed photovoltaic cells with unprecedented power conversion efficiencies and high stability equal to or even greater than those of today's best thin-film photovoltaic devices. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFShtbzL& md5=d00fae216daa9b428f9d38d97d7e2079 48. 48 Nocera, D. G. The artificial leaf. Acc. Chem. Res. 2012, 45, 767- 776, DOI: 10.1021/ar2003013 [ACS Full Text ACS Full Text], [CAS], Google Scholar 48 The Artificial Leaf Nocera, Daniel G. Accounts of Chemical Research (2012), 45 (5), 767-776CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society) A review. To convert the energy of sunlight into chem. energy, the leaf splits H2O via the photosynthetic process to produce mol. O and H, which is in a form of sepd. protons and electrons. The primary steps of natural photosynthesis involve the absorption of sunlight and its conversion into spatially sepd. electron-hole pairs. The holes of this wireless current are captured by the O evolving complex (OEC) of photosystem II (PSII) to oxidize H2O to O. The electrons and protons produced as a byproduct of the OEC reaction are captured by ferrodoxin of photosystem I. With the aid of ferrodoxin-NADP+ reductase, they are used to produce H as NADPH. For a synthetic material to realize the solar energy conversion function of the leaf, the light-absorbing material must capture a solar photon to generate a wireless current that is harnessed by catalysts, which drive the 4 electron/ hole fuel-forming H2O-splitting reaction under benign conditions and under 1 sun (100 mW/cm2) illumination. This Account describes the construction of an artificial leaf comprising earth-abundant elements by interfacing a triple junction, amorphous Si photovoltaic with H- and O-evolving catalysts made from a ternary alloy (NiMoZn) and a Co-phosphate cluster (Co-OEC), resp. The latter captures the structural and functional attributes of the PSII-OEC. Similar to the PSII-OEC, the Co-OEC self-assembles upon oxidn. of an earth-abundant metal ion from 2+ to 3+, may operate in natural H2O at room temp., and is self-healing. The Co-OEC also activates H2O by a p-coupled electron transfer mechanism in which the Co-OEC is increased by 4 hole equiv. akin to the S-state pumping of the Kok cycle of PSII. X-ray absorption spectroscopy studies established that the Co-OEC is a structural relative of Mn3CaO4-Mn cubane of the PSII-OEC, where Co replaces Mn and the cubane is extended in a corner-sharing, head-to-tail dimer. The ability to perform the O-evolving reaction in H2O at neutral or near-neutral conditions has several consequences for the construction of the artificial leaf. The NiMoZn alloy may be used in place of Pt to generate H. To stabilize Si in H2O, its surface is coated with a conducting metal oxide onto which the Co-OEC may be deposited. The net result is that immersing a triple-junction Si wafer coated with NiMoZn and Co-OEC in H2O and holding it up to sunlight can effect direct solar energy conversion via H2O splitting. By constructing a simple, stand-alone device composed of earth-abundant materials, the artificial leaf provides a means for an inexpensive and highly distributed solar-to-fuels system that employs low-cost systems engineering and manufg. Through this type of system, solar energy can become a viable energy supply to those in the non-legacy world. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC38XltVylu7k%253D&md5= c7ae917b44e8c4be8a38bf2be8f384d0 49. 49 Reece, S. Y. Wireless solar water splitting using silicon-based semiconductors and earth-abundant catalysts. Science 2011, 334, 645- 648, DOI: 10.1126/science.1209816 [Crossref], [PubMed], [CAS], Google Scholar 49 Wireless Solar Water Splitting Using Silicon-Based Semiconductors and Earth-Abundant Catalysts Reece, Steven Y.; Hamel, Jonathan A.; Sung, Kimberly; Jarvi, Thomas D.; Esswein, Arthur J.; Pijpers, Joep J. H.; Nocera, Daniel G. Science (Washington, DC, United States) (2011), 334 (6056), 645-648CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science) We describe the development of solar water-splitting cells comprising earth-abundant elements that operate in near-neutral pH conditions, both with and without connecting wires. The cells consist of a triple junction, amorphous silicon photovoltaic interfaced to hydrogen- and oxygen-evolving catalysts made from an alloy of earth-abundant metals and a cobalt-borate catalyst, resp. The devices described here carry out the solar-driven water-splitting reaction at efficiencies of 4.7% for a wired configuration and 2.5% for a wireless configuration when illuminated with 1 sun (100 mW per square centimeter) of air mass 1.5 simulated sunlight. Fuel-forming catalysts interfaced with light-harvesting semiconductors afford a pathway to direct solar-to-fuels conversion that captures many of the basic functional elements of a leaf. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtlyqu7vF& md5=f7bb658892c9c78d7a9d8f011c73a7b1 50. 50 Sharifi, T. Toward a Low-Cost Artificial Leaf: Driving Carbon-Based and Bifunctional Catalyst Electrodes with Solution-Processed Perovskite Photovoltaics. Adv. Energy Mater. 2016, 6, 1600738, DOI: 10.1002/aenm.201600738 [Crossref], Google Scholar There is no corresponding record for this reference. 51. 51 Li, Z. Hybrid Perovskite-Organic Flexible Tandem Solar Cell Enabling Highly Efficient Electrocatalysis Overall Water Splitting. Adv. Energy Mater. 2020, 10, 2000361, DOI: 10.1002/aenm.202000361 [Crossref], [CAS], Google Scholar 51 Hybrid Perovskite-Organic Flexible Tandem Solar Cell Enabling Highly Efficient Electrocatalysis Overall Water Splitting Li, Zhen; Wu, Shengfan; Zhang, Jie; Lee, Ka Chun; Lei, Hang; Lin, Francis; Wang, Zilong; Zhu, Zonglong; Jen, Alex K. Y. Advanced Energy Materials (2020), 10 (18), 2000361CODEN: ADEMBC; ISSN:1614-6840. (Wiley-Blackwell) Perovskite-org. tandem solar cells are attracting more attention due to their potential for highly efficient and flexible photovoltaic device. In this work, efficient perovskite-org. monolithic tandem solar cells integrating the wide bandgap perovskite (1.74 eV) and low bandgap org. active PBDB-T:SN6IC-4F (1.30 eV) layer, which serve as the top and bottom subcell, resp., are developed. The resulting perovskite-org. tandem solar cells with passivated wide-bandgap perovskite show a remarkable power conversion efficiency (PCE) of 15.13%, with an open-circuit voltage (Voc) of 1.85 V, a short-circuit photocurrent (Jsc) of 11.52 mA cm-2, and a fill factor (FF) of 70.98%. Thanks to the advantages of low temp. fabrication processes and the flexibility properties of the device, a flexible tandem solar cell which obtain a PCE of 13.61%, with Voc of 1.80 V, Jsc of 11.07 mA cm-2, and FF of 68.31% is fabricated. Moreover, to demonstrate the achieved high Voc in the tandem solar cells for potential applications, a photovoltaic (PV)-driven electrolysis system combing the tandem solar cell and water splitting electrocatalysis is assembled. The integrated device demonstrates a solar-to-hydrogen efficiency of 12.30% and 11.21% for rigid, and flexible perovskite-org. tandem solar cell based PV-driven electrolysis systems, resp. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BB3cXlt1ChtLk%253D&md5= e13b988660194a3ace033622a339a576 52. 52 Karuturi, S. K. Over 17% Efficiency Stand-Alone Solar Water Splitting Enabled by Perovskite-Silicon Tandem Absorbers. Adv. Energy Mater. 2020, 10, 2000772, DOI: 10.1002/ aenm.202000772 [Crossref], [CAS], Google Scholar 52 Over 17% Efficiency Stand-Alone Solar Water Splitting Enabled by Perovskite-Silicon Tandem Absorbers Karuturi, Siva Krishna; Shen, Heping; Sharma, Astha; Beck, Fiona J.; Varadhan, Purushothaman; Duong, The; Narangari, Parvathala Reddy; Zhang, Doudou; Wan, Yimao; He, Jr-Hau; Tan, Hark Hoe; Jagadish, Chennupati; Catchpole, Kylie Advanced Energy Materials (2020), 10 (28), 2000772CODEN: ADEMBC; ISSN:1614-6840. (Wiley-Blackwell) Realizing solar-to-hydrogen (STH) efficiencies close to 20% using low-cost semiconductors remains a major step toward accomplishing the practical viability of photoelectrochem. (PEC) hydrogen generation technologies. Dual-absorber tandem cells combining inexpensive semiconductors are a promising strategy to achieve high STH efficiencies at a reasonable cost. Here, a perovskite photovoltaic biased silicon (Si) photoelectrode is demonstrated for highly efficient stand-alone solar water splitting. A p+nn+ -Si/Ti/Pt photocathode is shown to present a remarkable photon-to-current efficiency of 14.1% under biased condition and stability over three days under continuous illumination. Upon pairing with a semitransparent mixed perovskite solar cell of an appropriate bandgap with state-of-the-art performance, an unprecedented 17.6% STH efficiency is achieved for self-driven solar water splitting. Modeling and anal. of the dual-absorber PEC system reveal that further work into replacing the noble-metal catalyst materials with earth-abundant elements and improvement of perovskite fill factor will pave the way for the realization of a low-cost high-efficiency PEC system. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtFCis7jM& md5=c44743dde681fa5593e1e9ee9d773274 53. 53 Luo, J. Water photolysis at 12.3% efficiency via perovskite photovoltaics and Earth-abundant catalysts. Science 2014, 345 , 1593- 1596, DOI: 10.1126/science.1258307 [Crossref], [PubMed], [CAS], Google Scholar 53 Water photolysis at 12.3% efficiency via perovskite photovoltaics and Earth-abundant catalysts Luo, Jingshan; Im, Jeong-Hyeok; Mayer, Matthew T.; Schreier, Marcel; Nazeeruddin, Mohammad Khaja; Park, Nam-Gyu; Tilley, S. David; Fan, Hong Jin; Graetzel, Michael Science (Washington, DC, United States) (2014), 345 (6204), 1593-1596CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science) Although sunlight-driven H2O splitting is a promising route to sustainable H fuel prodn., widespread implementation is hampered by the expense of the necessary photovoltaic and photoelectrochem. app. Here, the authors describe a highly efficient and low-cost H2O-splitting cell combining a state-of-the-art soln.-processed perovskite tandem solar cell and a bifunctional Earth-abundant catalyst. The catalyst electrode, a NiFe layered double hydroxide, exhibits high activity toward both the O and H evolution reactions in alk. electrolyte. The combination of the 2 yields a H2O-splitting photocurrent d. of ~10 mA per square centimeter, corresponding to a solar-to-H efficiency of 12.3%. Currently, the perovskite instability limits the cell lifetime. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhsFygtbbJ& md5=2db34619748164992665db7ab6b53914 54. 54 Luo, J. Bipolar Membrane-Assisted Solar Water Splitting in Optimal pH. Adv. Energy Mater. 2016, 6, 1600100, DOI: 10.1002/aenm.201600100 [Crossref], Google Scholar There is no corresponding record for this reference. 55. 55 Zou, X.; Zhang, Y. Noble metal-free hydrogen evolution catalysts for water splitting. Chem. Soc. Rev. 2015, 44, 5148 - 5180, DOI: 10.1039/C4CS00448E [Crossref], [PubMed], [CAS], Google Scholar 55 Noble metal-free hydrogen evolution catalysts for water splitting Zou, Xiaoxin; Zhang, Yu Chemical Society Reviews (2015), 44 (15), 5148-5180CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry) Sustainable hydrogen prodn. is an essential prerequisite of a future hydrogen economy. Water electrolysis driven by renewable resource-derived electricity and direct solar-to-hydrogen conversion based on photochem. and photoelectrochem. water splitting are promising pathways for sustainable hydrogen prodn. All these techniques require, among many things, highly active noble metal-free hydrogen evolution catalysts to make the water splitting process more energy-efficient and economical. In this review, we highlight the recent research efforts toward the synthesis of noble metal-free electrocatalysts, esp. at the nanoscale, and their catalytic properties for the hydrogen evolution reaction (HER). We review several important kinds of heterogeneous non-precious metal electrocatalysts, including metal sulfides, metal selenides, metal carbides, metal nitrides, metal phosphides, and heteroatom-doped nanocarbons. In the discussion, emphasis is given to the synthetic methods of these HER electrocatalysts, the strategies of performance improvement, and the structure/compn.-catalytic activity relationship. We also summarize some important examples showing that non-Pt HER electrocatalysts could serve as efficient cocatalysts for promoting direct solar-to-hydrogen conversion in both photochem. and photoelectrochem. water splitting systems, when combined with suitable semiconductor photocatalysts. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2MXms1ygtbo%253D&md5= ac5b0a548bab69f1e7a05520c8f1ced2 56. 56 Boyd, C. C.; Cheacharoen, R.; Leijtens, T.; McGehee, M. D. Understanding Degradation Mechanisms and Improving Stability of Perovskite Photovoltaics. Chem. Rev. 2019, 119, 3418- 3451 , DOI: 10.1021/acs.chemrev.8b00336 [ACS Full Text ACS Full Text], [CAS], Google Scholar 56 Understanding Degradation Mechanisms and Improving Stability of Perovskite Photovoltaics Boyd, Caleb C.; Cheacharoen, Rongrong; Leijtens, Tomas; McGehee, Michael D. Chemical Reviews (Washington, DC, United States) (2019), 119 (5), 3418-3451CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society) This review article examines the current state of understanding in how metal halide perovskite solar cells can degrade when exposed to moisture, oxygen, heat, light, mech. stress, and reverse bias. It also highlights strategies for improving stability, such as tuning the compn. of the perovskite, introducing hydrophobic coatings, replacing metal electrodes with carbon or transparent conducting oxides, and packaging. The article concludes with recommendations on how accelerated testing should be performed to rapidly develop solar cells that are both extraordinarily efficient and stable. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXit1Smt7fL& md5=31d99d3f1b29ccacdba83624b84b3c54 57. 57 Juarez-Perez, E. J. Photodecomposition and thermal decomposition in methylammonium halide lead perovskites and inferred design principles to increase photovoltaic device stability. J. Mater. Chem. A 2018, 6, 9604- 9612, DOI: 10.1039/C8TA03501F [Crossref], [CAS], Google Scholar 57 Photodecomposition and thermal decomposition in methylammonium halide lead perovskites and inferred design principles to increase photovoltaic device stability Juarez-Perez, Emilio J.; Ono, Luis K.; Maeda, Maki; Jiang, Yan; Hawash, Zafer; Qi, Yabing Journal of Materials Chemistry A: Materials for Energy and Sustainability (2018), 6 (20), 9604-9612CODEN: JMCAET; ISSN: 2050-7496. (Royal Society of Chemistry) Hybrid lead halide perovskites have emerged as promising active materials for photovoltaic cells. Although superb efficiencies have been achieved, it is widely recognized that long-term stability is a key challenge intimately detg. the future development of perovskite-based photovoltaic technol. Herein, we present reversible and irreversible photodecompn. reactions of methylammonium lead iodide (MAPbI3). Simulated sunlight irradn. and temp. (40-80 degC) corresponding to solar cell working conditions lead to three degrdn. pathways: (1) CH3NH2 + HI (identified as the reversible path), (2) NH3 + CH3I (the irreversible or detrimental path), and (3) a reversible Pb(0) + I2(g) photodecompn. reaction. If only the reversible reactions (1) and (3) take place and reaction (2) can be avoided, encapsulated MAPbI3 can be regenerated during the off-illumination timeframe. Therefore, to further improve operational stability in hybrid perovskite solar cells, detailed understanding of how to mitigate photodegrdn. and thermal degrdn. processes is necessary. First, encapsulation of the device is necessary not only to avoid contact of the perovskite with ambient air, but also to prevent leakage of volatile products released from the perovskite. Second, careful selection of the org. cations in the compositional formula of the perovskite is necessary to avoid irreversible reactions. Third, selective contacts must be as chem. inert as possible toward the volatile released products. Finally, hybrid halide perovskite materials are speculated to undergo a dynamic formation and decompn. process; this can gradually decrease the cryst. grain size of the perovskite with time; therefore, efforts to deposit highly cryst. perovskites with large crystal sizes may fail to increase the long-term stability of photovoltaic devices. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC1cXotF2isrY%253D&md5= d336b7d9a747eec1e988e066cd7ab159 58. 58 Ciccioli, A.; Latini, A. Thermodynamics and the Intrinsic Stability of Lead Halide Perovskites CH3NH3PbX3. J. Phys. Chem. Lett. 2018, 9, 3756- 3765, DOI: 10.1021/ acs.jpclett.8b00463 [ACS Full Text ACS Full Text], [CAS], Google Scholar 58 Thermodynamics and the Intrinsic Stability of Lead Halide Perovskites CH3NH3PbX3 Ciccioli, Andrea; Latini, Alessandro Journal of Physical Chemistry Letters (2018), 9 (13), 3756-3765CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society) The role of thermodn. in assessing the intrinsic instability of the MeNH3PbX3 perovskites (X = Cl,Br,I) is outlined from the available exptl. information. Possible decompn./degrdn. pathways driven by the inherent instability of the material are considered. The decompn. to precursors MeNH3X(s) and PbX2 (s) is 1st analyzed, pointing out the importance of both the enthalpic and the entropic factor, the latter playing a stabilizing role making the stability higher than often asserted. For MeNH3PbI3, the disagreement between the available calorimetric results makes the stability prediction uncertain. Subsequently, the gas-releasing decompn. paths are discussed, with emphasis on the discrepant results presently available, probably reflecting the predominance of thermodn. or kinetic control. The competition between the formation of NH3(g) + MeX(g), MeNH2(g) + HX(g) or MeNH3X(g) is analyzed, in comparison with the thermal decompn. of methylammonium halides. In view of the scarce and inconclusive thermodn. studies to-date available, the need for further exptl. data is emphasized. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtFeisrvI& md5=58763d57fdcef06be34aa2834609ef14 59. 59 Samu, G. F.; Janaky, C.; Kamat, P. V. A Victim of Halide Ion Segregation. How Light Soaking Affects Solar Cell Performance of Mixed Halide Lead Perovskites. ACS Energy Letters 2017, 2, 1860- 1861, DOI: 10.1021/acsenergylett.7b00589 [ACS Full Text ACS Full Text], [CAS], Google Scholar 59 A Victim of Halide Ion Segregation. How Light Soaking Affects Solar Cell Performance of Mixed Halide Lead Perovskites Samu, Gergely F.; Janaky, Csaba; Kamat, Prashant V. ACS Energy Letters (2017), 2 (8), 1860-1861CODEN: AELCCP; ISSN:2380-8195. (American Chemical Society) Photoinduced segregation in mixed halide perovskites has a direct influence on decreasing the solar cell efficiency as segregated I-rich domains serve as charge recombination centers. The changes in the external quantum efficiency mirror the spectral loss in the absorption; however, the time scale of the IPCE recovery in the dark is slower than the absorption recovery, showing the intricate nature of the photoinduced halide segregation and charge collection in solar cell devices. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXht1Wku7bP& md5=023d6b709c4c9cd1b91e2b90d7c4acc3 60. 60 Latini, A.; Gigli, G.; Ciccioli, A. A study on the nature of the thermal decomposition of methylammonium lead iodide perovskite, CH3NH3PbI3: an attempt to rationalise contradictory experimental results. Sustainable Energy & Fuels 2017, 1, 1351- 1357, DOI: 10.1039/C7SE00114B [Crossref], [CAS], Google Scholar 60 A study on the nature of the thermal decomposition of methylammonium lead iodide perovskite, CH3NH3PbI3: an attempt to rationalise contradictory experimental results Latini, Alessandro; Gigli, Guido; Ciccioli, Andrea Sustainable Energy & Fuels (2017), 1 (6), 1351-1357CODEN: SEFUA7; ISSN:2398-4902. (Royal Society of Chemistry) The nature of the gas phase product released during the thermal decompn. of CH3NH3PbI3 (methylammonium lead iodide) to PbI2 (lead diiodide) under vacuum is discussed on the basis of thermodn. predictions, recently published exptl. results, and new expts. presented here. From the limited data currently available, the nature of the main decompn. path is not clear because, both, the process releasing HI(g) + CH3NH2 (g) and that leading to NH3(g) + CH3I(g) were obsd. under different conditions. Our thermodn. anal. showed that process is largely favored for all the CH3NH3PbX3 (X = Cl, Br, I) compds. However, Knudsen effusion mass spectrometry expts. (temp. range 140-240 degC) showed that HI(g) and CH3NH2(g) were the predominant species in the vapor, with process occurring to a much smaller extent than suggested by the thermodn. driving force, thus being of minor importance under effusion conditions. We also found that this process was comparatively enhanced by high temps. and low effusion rates (high impedance orifice). Our exptl. evidence suggested that the thermodynamically favored process was affected by a significant kinetic hindrance. Overall, the prevailing decompn. path is likely to markedly depend on the actual operative conditions. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhs1CrsLrL& md5=c942e4c428cd439c6f0d65b304522ea2 61. 61 Shao, Y. Grain boundary dominated ion migration in polycrystalline organic-inorganic halide perovskite films. Energy Environ. Sci. 2016, 9, 1752- 1759, DOI: 10.1039/ C6EE00413J [Crossref], [CAS], Google Scholar 61 Grain boundary dominated ion migration in polycrystalline organic-inorganic halide perovskite films Shao, Yuchuan; Fang, Yanjun; Li, Tao; Wang, Qi; Dong, Qingfeng; Deng, Yehao; Yuan, Yongbo; Wei, Haotong; Wang, Meiyu; Gruverman, Alexei; Shield, Jeffery; Huang, Jinsong Energy & Environmental Science (2016), 9 (5), 1752-1759CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry) The efficiency of perovskite solar cells is approaching that of single-cryst. silicon solar cells despite the presence of a large grain boundary (GB) area in the polycryst. thin films. Here, by using a combination of nanoscopic and macroscopic level measurements, we show that ion migration in polycryst. perovskites dominates through GBs. Atomic force microscopy measurements reveal much stronger hysteresis both for photocurrent and dark-current at the GBs than on the grain interiors, which can be explained by faster ion migration at the GBs. The dramatically enhanced ion migration results in the redistribution of ions along the GBs after elec. poling, in contrast to the intact grain area. The perovskite single-crystal devices without GBs show negligible current hysteresis and no ion-migration signal. The discovery of dominating ion migration through GBs in perovskites can lead to broad applications in many types of devices including photovoltaics, memristors, and ion batteries. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC28XksFKmsrc%253D&md5= 134dde4b7e9fae67f7d845a8918d30f5 62. 62 Juarez-Perez, E. J.; Hawash, Z.; Raga, S. R.; Ono, L. K.; Qi, Y. Thermal degradation of CH3NH3PbI3 perovskite into NH3 and CH3I gases observed by coupled thermogravimetry-mass spectrometry analysis. Energy Environ. Sci. 2016, 9, 3406- 3410, DOI: 10.1039/C6EE02016J [Crossref], [CAS], Google Scholar 62 Thermal degradation of CH3NH3PbI3 perovskite into NH3 and CH3I gases observed by coupled thermogravimetry-mass spectrometry analysis Juarez-Perez, Emilio J.; Hawash, Zafer; Raga, Sonia R.; Ono, Luis K.; Qi, Yabing Energy & Environmental Science (2016), 9 (11), 3406-3410 CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry) Thermal gravimetric and DTA (TG-DTA) coupled with quadrupole mass spectrometry (MS) and first principles calcns. were employed to elucidate the chem. nature of released gases during the thermal decompn. of CH3NH3PbI3. In contrast to the common wisdom that CH3NH3PbI3 is decompd. into CH3NH2 and HI, the major gases were methyliodide (CH3I) and ammonia (NH3). We anticipate that our findings will provide new insights into further formulations of the perovskite active material and device design that can prevent methylammonium decompn. and thus increase the long-term stability of perovskite-based optoelectronic devices. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsVKjtLjM& md5=c6c03d9dbf93e71a54a56d5cf9d7f000 63. 63 Brunetti, B.; Cavallo, C.; Ciccioli, A.; Gigli, G.; Latini, A. On the Thermal and Thermodynamic (In)Stability of Methylammonium Lead Halide Perovskites. Sci. Rep. 2016, 6, 31896, DOI: 10.1038/srep31896 [Crossref], [PubMed], [CAS], Google Scholar 63 On the Thermal and Thermodynamic (In)Stability of Methylammonium Lead Halide Perovskites Brunetti, Bruno; Cavallo, Carmen; Ciccioli, Andrea; Gigli, Guido; Latini, Alessandro Scientific Reports (2016), 6 (), 31896CODEN: SRCEC3; ISSN: 2045-2322. (Nature Publishing Group) The interest of the scientific community on methylammonium lead halide perovskites (MAPbX3, X = Cl, Br, I) for hybrid org.-inorg. solar cells has grown exponentially since the first report in 2009. This fact is clearly justified by the very high efficiencies attainable (reaching 20% in lab scale devices) at a fraction of the cost of conventional photovoltaics. However, many problems must be solved before a market introduction of these devices can be envisaged. Perhaps the most important to be addressed is the lack of information regarding the thermal and thermodn. stability of the materials towards decompn., which are intrinsic properties of them and which can seriously limit or even exclude their use in real devices. In this work we present and discuss the results we obtained using non-ambient X-ray diffraction, Knudsen effusion-mass spectrometry (KEMS) and Knudsen effusion mass loss (KEML) techniques on MAPbCl3, MAPbBr3 and MAPbI3. The measurements demonstrate that all the materials decomp. to the corresponding solid lead (II) halide and gaseous methylamine and hydrogen halide, and the decompn. is well detectable even at moderate temps. (~60 degC). Our results suggest that these materials may be problematic for long term operation of solar devices. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsVSrsb7N& md5=531e2461d5fd57c414ad5d9959bbd25c 64. 64 Zhang, Y. Charge selective contacts, mobile ions and anomalous hysteresis in organic-inorganic perovskite solar cells. Mater. Horiz. 2015, 2, 315- 322, DOI: 10.1039/ C4MH00238E [Crossref], [CAS], Google Scholar 64 Charge selective contacts, mobile ions and anomalous hysteresis in organic-inorganic perovskite solar cells Zhang, Ye; Liu, Mingzhen; Eperon, Giles E.; Leijtens, Tomas C.; McMeekin, David; Saliba, Michael; Zhang, Wei; de Bastiani, Michele; Petrozza, Annamaria; Herz, Laura M.; Johnston, Michael B.; Lin, Hong; Snaith, Henry J. Materials Horizons (2015), 2 (3), 315-322CODEN: MHAOBM; ISSN: 2051-6355. (Royal Society of Chemistry) High-efficiency perovskite solar cells typically employ an org.-inorg. metal halide perovskite material as light absorber and charge transporter, sandwiched between a p-type electron-blocking org. hole-transporting layer and an n-type hole-blocking electron collection titania compact layer. Some device configurations also include a thin mesoporous layer of TiO2 or Al2O3 which is infiltrated and capped with the perovskite absorber. Herein, we demonstrate that it is possible to fabricate planar and mesoporous perovskite solar cells devoid of an electron selective hole-blocking titania compact layer, which momentarily exhibit power conversion efficiencies (PCEs) of over 13%. This performance is however not sustained and is related to the previously obsd. anomalous hysteresis in perovskite solar cells. The "compact layer-free" meso-superstructured perovskite devices yield a stabilized PCE of only 2.7% while the compact layer-free planar heterojunction devices display no measurable steady state power output when devoid of an electron selective contact. In contrast, devices including the titania compact layer exhibit stabilized efficiency close to that derived from the current voltage measurements. We propose that under forward bias the perovskite diode becomes polarised, providing a beneficial field, allowing accumulation of pos. and neg. space charge near the contacts, which enables more efficient charge extn. This provides the required built-in potential and selective charge extn. at each contact to temporarily enable efficient operation of the perovskite solar cells even in the absence of charge selective n- and p-type contact layers. The polarisation of the material is consistent with long range migration and accumulation of ionic species within the perovskite to the regions near the contacts. When the external field is reduced under working conditions, the ions can slowly diffuse away from the contacts redistributing throughout the film, reducing the field asymmetry and the effectiveness of the operation of the solar cells. We note that in light of recent publications showing high efficiency in devices devoid of charge. selective contacts, this work reaffirms the abs. necessity to measure and report the stabilized power output under load when characterizing perovskite solar cells. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2MXjs1Kntb8%253D&md5= 3af138d227ee0f69d7e253ee29d8732e 65. 65 Han, Y. Degradation observations of encapsulated planar CH3NH3PbI3 perovskite solar cells at high temperatures and humidity. J. Mater. Chem. A 2015, 3, 8139- 8147, DOI: 10.1039/C5TA00358J [Crossref], [CAS], Google Scholar 65 Degradation observations of encapsulated planar CH3NH3PbI3 perovskite solar cells at high temperatures and humidity Han, Yu; Meyer, Steffen; Dkhissi, Yasmina; Weber, Karl; Pringle, Jennifer M.; Bach, Udo; Spiccia, Leone; Cheng, Yi-Bing Journal of Materials Chemistry A: Materials for Energy and Sustainability (2015), 3 (15), 8139-8147CODEN: JMCAET; ISSN: 2050-7496. (Royal Society of Chemistry) The stability of encapsulated planar-structured CH3NH3PbI3 (MAPbI3) perovskite solar cells (PSCs) was investigated under various simulated environmental conditions. The tests were performed under approx. one sun (100 mW cm-2) illumination, varying temp. (up to 85 degC cell temp.) and humidity (up to 80%). The application of advanced sealing techniques improved the device stability, but all devices showed significant degrdn. after prolonged aging at high temp. and humidity. The degrdn. mechanism was studied by post-mortem anal. of the disassembled cells using SEM and XRD. This revealed that the degrdn. was mainly due to the decompn. of MAPbI3, as a result of reaction with H2O, and the subsequent reaction of hydroiodic acid, formed during MAPbI3 decompn., with the silver back contact electrode layer. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2MXjvF2ktLo%253D&md5= eeb439adec1eafcc54e12bb16726305a 66. 66 Azpiroz, J. M.; Mosconi, E.; Bisquert, J.; De Angelis, F. Defect migration in methylammonium lead iodide and its role in perovskite solar cell operation. Energy Environ. Sci. 2015 , 8, 2118- 2127, DOI: 10.1039/C5EE01265A [Crossref], [CAS], Google Scholar 66 Defect migration in methylammonium lead iodide and its role in perovskite solar cell operation Azpiroz, Jon M.; Mosconi, Edoardo; Bisquert, Juan; De Angelis, Filippo Energy & Environmental Science (2015), 8 (7), 2118-2127CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry) In spite of the unprecedented advance of organohalide lead perovskites in the photovoltaics scenario, many of the characteristics of this class of materials, including their slow photocond. response, solar cell hysteresis, and switchable photocurrent, remain poorly understood. Many exptl. hints point to defect migration as a plausible mechanism underlying these anomalous properties. By means of state-of-the-art first-principles computational analyses carried out on the tetragonal MAPbI3 (MA = methylammonium) perovskite and on its interface with TiO2, we demonstrate that iodine vacancies and interstitials may easily diffuse across the perovskite crystal, with migration activation energies as low as ~0.1 eV. Under working conditions, iodine-related defects are predicted to migrate at the electrodes on very short time scales (<1 ms). MA and Pb vacancies, with calcd. activation barriers of ~0.5 and 0.8 eV, resp., could be responsible for the slow response inherent to perovskites, with typical calcd. migration times of the order of tens of ms to minutes. By investigating realistic models of the perovskite/TiO2 interface we show that neg. charged defects, e.g. MA vacancies, close to the electron transport layer (TiO2 in our case) modify the perovskite electronic state landscape, hampering charge extn. at selective contacts, thus possibly contributing to the obsd. solar cell hysteresis. We further demonstrate the role of the electron transport layer in affecting the initial concn. of defects close to the selective contacts, highlighting how charge sepn. at the perovskite/TiO2 interface may further change the defect distribution. We believe that this work, identifying the mobile species in perovskite solar cells, their migration across the perovskite material, and their effect on the operational mechanism of the device, may pave the way for the development of new materials and solar cell architectures with improved and stabilized efficiencies. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2MXpt1Sltb4%253D&md5= 147424f62f1c428388260b31bad958ae 67. 67 Svanstrom, S. Degradation Mechanism of Silver Metal Deposited on Lead Halide Perovskites. ACS Appl. Mater. Interfaces 2020, 12, 7212- 7221, DOI: 10.1021/acsami.9b20315 [ACS Full Text ACS Full Text], [CAS], Google Scholar 67 Degradation Mechanism of Silver Metal Deposited on Lead Halide Perovskites Svanstrom Sebastian; Rensmo Hakan; Jacobsson T Jesper; Boschloo Gerrit; Johansson Erik M J; Cappel Ute B ACS applied materials & interfaces (2020), 12 (6), 7212-7221 ISSN:. Lead halide perovskite solar cells have significantly increased in both efficiency and stability over the last decade. An important aspect of their long-term stability is the reaction between the perovskite and other materials in the solar cell. This includes the contact materials and their degradation if they can potentially come into contact through, e.g., pinholes or material diffusion and migration. Here, we explore the interactions of silver contacts with lead halide perovskites of different compositions by using a model system where thermally evaporated silver was deposited directly on the surface of the perovskites. Using X-ray photoelectron spectroscopy with support from scanning electron microscopy, X-ray diffraction, and UV-visible absorption spectroscopy, we studied the film formation and degradation of silver on perovskites with different compositions. The deposited silver does not form a continuous silver film but instead tends to form particles on a bare perovskite surface. These particles are initially metallic in character but degrade into AgI and AgBr over time. The degradation and migration appear unaffected by the replacement of methylammonium with cesium but are significantly slowed down by the complete replacement of iodide with bromide. The direct contact between silver and the perovskite also significantly accelerates the degradation of the perovskite, with a significant loss of organic cations and the possible formation of PbO, and, at the same time, changed the surface morphology of the iodide-rich perovskite interface. Our results further indicate that an important degradation pathway occurred through gas-phase perovskite degradation products. This highlights the importance of control over the interface materials and the use of completely hermetical barrier layers for the long-term stability and therefore the commercial viability of silver electrodes. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A280%3ADC%252BB38%252FitFCmuw%253D%253D&md5= c8e316ffb621703560a2e7664eeabe2c 68. 68 Li, G.-R.; Gao, X.-P. Low-Cost Counter-Electrode Materials for Dye-Sensitized and Perovskite Solar Cells. Adv. Mater. 2020, 32, 1806478, DOI: 10.1002/adma.201806478 [Crossref], [CAS], Google Scholar 68 Low-Cost Counter-Electrode Materials for Dye-Sensitized and Perovskite Solar Cells Li, Guo-Ran; Gao, Xue-Ping Advanced Materials (Weinheim, Germany) (2020), 32 (3), 1806478CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA) A review. It is un-doubtable that the use of solar energy will continue to increase. Solar cells that convert solar energy directly to electricity are one of the most convenient and important photoelec. conversion devices. Though silicon-based solar cells and thin-film solar cells have been commercialized, developing low-cost and highly efficient solar cells to meet future needs is still a long-term challenge. Some emerging solar-cell types, such as dye-sensitized and perovskite, are approaching acceptable performance levels, but their costs remain too high. To obtain a higher performance-price ratio, it is necessary to find new low-cost counter materials to replace conventional precious metal electrodes (Pt, Au, and Ag) in these emerging solar cells. In recent years, the no. of counter-electrode materials available, and their scope for further improvement, has expanded for dye-sensitized and perovskite solar cells. Generally regular patterns in the intrinsic features and structural design of counter materials for emerging solar cells, in particular from an electrochem. perspective and their effects on cost and efficiency, are explored. It is hoped that this recapitulative anal. will help to make clear what has been achieved and what still remains for the development of cost-effective counter-electrode materials in emerging solar cells. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC1MXhtVejtb%252FF&md5= 02958aaaf8d9397fd1c86fd26c954b31 69. 69 Zhang, Y.; Ng, S.-W.; Lu, X.; Zheng, Z. Solution-Processed Transparent Electrodes for Emerging Thin-Film Solar Cells. Chem. Rev. 2020, 120, 2049- 2122, DOI: 10.1021/ acs.chemrev.9b00483 [ACS Full Text ACS Full Text], [CAS], Google Scholar 69 Solution-Processed Transparent Electrodes for Emerging Thin-Film Solar Cells Zhang, Yaokang; Ng, Sze-Wing; Lu, Xi; Zheng, Zijian Chemical Reviews (Washington, DC, United States) (2020), 120 (4), 2049-2122CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society) A review. Soln.-processed solar cells are appealing because of the low manufg. cost, the good compatibility with flexible substrates, and the ease of large-scale fabrication. Whereas soln.-processable active materials have been widely adopted for the fabrication of org., dye-sensitized, and perovskite solar cells, vacuum-deposited transparent conducting oxides (TCOs) such as indium tin oxide, fluorine-doped tin oxide, and aluminum-doped tin oxide are still the most frequently used transparent electrodes (TEs) for solar cells. These TCOs not only significantly increase the manufg. cost of the device, but also are too brittle for future flexible and wearable applications. Therefore, developing soln.-processed TEs for solar cells is of great interest. This paper provides a detailed discussion on the recent development of soln.-processed TEs, including the chem. synthesis of the electrode materials, the soln.-based technologies for the electrode fabrication, the optical and elec. properties of the soln.-processed TEs, and their applications on solar cells. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BB3cXht1CqsLc%253D&md5= d8f4cc9fdae2ce98782e7fca700cb8f5 70. 70 Zhang, J. The Role of 3D Molecular Structural Control in New Hole Transport Materials Outperforming Spiro-OMeTAD in Perovskite Solar Cells. Adv. Energy Mater. 2016, 6, 1601062, DOI: 10.1002/aenm.201601062 [Crossref], Google Scholar There is no corresponding record for this reference. 71. 71 Tan, H. Efficient and stable solution-processed planar perovskite solar cells via contact passivation. Science 2017, 355, 722- 726, DOI: 10.1126/science.aai9081 [Crossref], [PubMed], [CAS], Google Scholar 71 Efficient and stable solution-processed planar perovskite solar cells via contact passivation Tan, Hairen; Jain, Ankit; Voznyy, Oleksandr; Lan, Xinzheng; Garcia de Arquer, F. Pelayo; Fan, James Z.; Quintero-Bermudez, Rafael; Yuan, Mingjian; Zhang, Bo; Zhao, Yicheng; Fan, Fengjia; Li, Peicheng; Quan, Li Na; Zhao, Yongbiao; Lu, Zheng-Hong; Yang, Zhenyu; Hoogland, Sjoerd; Sargent, Edward H. Science (Washington, DC, United States) (2017), 355 (6326), 722-726CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science) Planar perovskite solar cells (PSCs) made entirely via soln. processing at low temps. (<150degC) offer promise for simple manufg., compatibility with flexible substrates, and perovskite-based tandem devices. However, these PSCs require an electron-selective layer that performs well with similar processing. We report a contact-passivation strategy using chlorine-capped TiO2 colloidal nanocrystal film that mitigates interfacial recombination and improves interface binding in low-temp. planar solar cells. We fabricated solar cells with certified efficiencies of 20.1 and 19.5% for active areas of 0.049 and 1.1 square centimeters, resp., achieved via low-temp. soln. processing. Solar cells with efficiency greater than 20% retained 90% (97% after dark recovery) of their initial performance after 500 h of continuous room-temp. operation at their max. power point under 1-sun illumination (where 1 sun is defined as the std. illumination at AM1.5, or 1 kW/square meter). >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2sXis1yjtbo%253D&md5= c902ae179ca74ae26c435fddaf61ed40 72. 72 Schmidt, T. M.; Larsen-Olsen, T. T.; Carle, J. E.; Angmo, D.; Krebs, F. C. Upscaling of Perovskite Solar Cells: Fully Ambient Roll Processing of Flexible Perovskite Solar Cells with Printed Back Electrodes. Adv. Energy Mater. 2015, 5, 1500569, DOI: 10.1002/aenm.201500569 [Crossref], Google Scholar There is no corresponding record for this reference. 73. 73 Sander, R. Compilation of Henry's law constants (version 4.0) for water as solvent. Atmos. Chem. Phys. 2015, 15, 4399- 4981 , DOI: 10.5194/acp-15-4399-2015 [Crossref], [CAS], Google Scholar 73 Compilation of Henry's law constants (version 4.0) for water as solvent Sander, R. Atmospheric Chemistry and Physics (2015), 15 (8), 4399-4981 CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications) Many atm. chems. occur in the gas phase as well as in liq. cloud droplets and aerosol particles. Therefore, it is necessary to understand the distribution between the phases. According to Henry's law, the equil. ratio between the abundances in the gas phase and in the aq. phase is const. for a dil. soln. Henry's law consts. of trace gases of potential importance in environmental chem. have been collected and converted into a uniform format. The compilation contains 17350 values of Henry's law consts. for 4632 species, collected from 689 refs. >> More from SciFinder ^(r) https://chemport.cas.org/services/resolver?origin=ACS& resolution=options&coi= 1%3ACAS%3A528%3ADC%252BC2MXotFyktrc%253D&md5= c06fd66b33b6dae9e50f0e9c1e3e60cb * Supporting Information Supporting Information ARTICLE SECTIONS Jump To ----------------------------------------------------------------- The Supporting Information is available free of charge at https:/ /pubs.acs.org/doi/10.1021/acssuschemeng.1c03565. + XPS, SEM, XRD, electrochemical characterization, solar cell performance measurements, PV-driven electrolysis performance measurements, and cost analysis (PDF) + sc1c03565_si_001.pdf (1.92 MB) Terms & Conditions Most electronic Supporting Information files are available without a subscription to ACS Web Editions. 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