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Data‐intensive discovery of water‐splitting catalysts can accelerate the development of sustainable energy technologies, such as the photocatalytic and/or electrocatalytic production of renewable hydrogen fuel. Through computational screening, 13 materials were recently predicted as potential water‐splitting photocatalysts: Cu3NbS4, CuYS2, SrCu2O2, CuGaO2, Na3BiO4, Sr2PbO4, LaCuOS, LaCuOSe, Na2TeO4, La4O4Se3, Cu2WS4, BaCu2O2, and CuAlO2. Herein, these materials are synthesized, their bandgaps and band alignments are experimentally determined, and their photoelectrocatalytic hydrogen evolution properties are assessed. Using cyclic voltammetry and chopped illumination experiments, 9 of the 13 materials are experimentally found to have bandgaps and band alignments that straddle the potentials required for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), as computationally predicted. During photocatalytic testing, 12 of the materials yield a measurable photocurrent. However, only three are found to be active for the HER, with Cu3NbS4, CuYS2, and Cu2WS4 producing H2 in amounts comparable to bare TiO2; a benchmark photocatalyst. This study provides experimental validation of computational bandgap and band alignment predictions while also successfully identifying active photocatalysts. [ABSTRACT FROM AUTHOR]

Topological materials have high carrier mobilities that can be maintained in the presence of crystal structure defects, which is useful for catalysis. Topological materials have been shown to be active catalysts, but it remains unclear if topology persists during catalysis. We studied the physical and chemical evolution of MoTe2 during photo‐ and electrocatalytic hydrogen production. This material offers a unique opportunity to directly compare a trivial semiconductor, 2H‐MoTe2, with a topological insulator, 1T'‐MoTe2, with comparable compositions, crystal structures, and surface roughnesses. We observed no major bulk changes in the materials after catalysis. The surfaces of the catalysts were significantly roughened and oxidized, but the carrier mobility of the topological phase remained high. These results suggest that topology persists during, and may be advantageous for, catalysis, and provide rationale for considering topology in the search for water‐splitting catalysts. [ABSTRACT FROM AUTHOR]

Alloying metals can achieve enhanced kinetics for the hydrogen evolution reaction (HER), but most known HER alloy catalysts combine metals that are miscible in the bulk. Theoretical studies suggest that bulk‐immiscible AgRh alloys will exhibit near‐zero hydrogen binding energies, which is important for high‐performing HER catalysts. Current routes to AgRh nanoparticles yield only small quantities or require specialized setups. Here, we establish a ligand‐free, scalable synthesis of AgRh nanoparticles and demonstrate their catalytic viability for the HER under acidic conditions. AgRh nanoparticle electrodes exhibited low operating potentials with current densities of −10 and −100 mA/cm2 at overpotentials of −17 and −32 mV, respectively. The electrodes were highly durable with very little change in overpotentials required to maintain hydrogen production for 24 h and after 400 successive cycles. These results establish bulk‐immiscible AgRh alloys as promising non‐Pt HER catalysts. [ABSTRACT FROM AUTHOR]

A fundamental understanding of the behavior of non-noble based materials toward the hydrogen evolution reaction is crucial for the successful implementation into practical devices. Through the implementation of a highly sensitive inductively coupled plasma mass spectrometer coupled to a scanning flow cell, the activity and stability of non-noble electrocatalysts is presented. The studied catalysts comprise a range of compositions, including metal carbides (WC), sulfides (MoS2), phosphides (Ni5P4, Co2P), and their base metals (W, Ni, Mo, Co); their activity, stability, and degradation behavior was elaborated and compared to the state-of-the-art catalyst platinum. The non-noble materials are stable at HER potentials but dissolve substantially when no current is flowing. Through pre- and post-characterization of the catalysts, explanations of their stability (thermodynamics and kinetics) are discussed, challenges for the application in real devices are analyzed, and strategies for circumventing dissolution are suggested. The precise correlation of metal dissolution with applied potential/current density allows for narrowing down suitable material choices as replacement for precious group metals as for example, platinum and opens up new ways in finding cost-efficient, active, and stable new-generation electrocatalysts. [ABSTRACT FROM AUTHOR]

Nanoparticles of cobalt phosphide, CoP, have been prepared and evaluated as electrocatalysts for the hydrogen evolution reaction (HER) under strongly acidic conditions (0.50 M H2SO4, pH 0.3). Uniform, multi-faceted CoP nanoparticles were synthesized by reacting Co nanoparticles with trioctylphosphine. Electrodes comprised of CoP nanoparticles on a Ti support (2 mg cm−2 mass loading) produced a cathodic current density of 20 mA cm−2 at an overpotential of −85 mV. The CoP/Ti electrodes were stable over 24 h of sustained hydrogen production in 0.50 M H2SO4. The activity was essentially unchanged after 400 cyclic voltammetric sweeps, suggesting long-term viability under operating conditions. CoP is therefore amongst the most active, acid-stable, earth-abundant HER electrocatalysts reported to date. [ABSTRACT FROM AUTHOR]

REFERENCE 1 H. Wang, R. Katz, J. Fanghanel, R. E. Schaak, and V. Gopalan, "Ultrasensitive electrode-free and co-catalyst-free detection of nanomoles per hour hydrogen evolution for the discovery of new photocatalysts", Rev. Sci. Instrum. Erratum: "Ultrasensitive electrode-free and co-catalyst-free detection of nanomoles per hour hydrogen evolution for the discovery of new photocatalysts" [Rev. Sci. Instrum. In the first paragraph of the original paper,[1] the sentence "Given that the Earth receives 3 × 10 SP -24 sp J of solar energy annually..." should be changed to "Given that the Earth receives 3 × 10 SP 24 sp J of solar energy annually...." In Eq. (2) of the paper, the format should be corrected to HT ht (2) The requested changes do not affect the main body of the work or compromise in anyway the conclusions of the article. [Extracted from the article]

Amorphous tungsten phosphide (WP), which has been synthesized as colloidal nanoparticles with an average diameter of 3 nm, has been identified as a new electrocatalyst for the hydrogen-evolution reaction (HER) in acidic aqueous solutions. WP/Ti electrodes produced current densities of -10 mA cm-2 and -20 mA cm-2 at overpotentials of only -120 mV and -140 mV, respectively, in 0.50 M H2SO4(aq). [ABSTRACT FROM AUTHOR]

Topological materials have high carrier mobilities that can be maintained in the presence of crystal structure defects, which is useful for catalysis. Topological materials have been shown to be active catalysts, but it remains unclear if topology persists during catalysis. We studied the physical and chemical evolution of MoTe2 during photo‐ and electrocatalytic hydrogen production. This material offers a unique opportunity to directly compare a trivial semiconductor, 2H‐MoTe2, with a topological insulator, 1T'‐MoTe2, with comparable compositions, crystal structures, and surface roughnesses. We observed no major bulk changes in the materials after catalysis. The surfaces of the catalysts were significantly roughened and oxidized, but the carrier mobility of the topological phase remained high. These results suggest that topology persists during, and may be advantageous for, catalysis, and provide rationale for considering topology in the search for water‐splitting catalysts. [ABSTRACT FROM AUTHOR]

Hydrogen gas obtained by the electrolysis of water has long been proposed as a clean and sustainable alternative to fossil fuels. Noble metals such as Pt are capable of splitting water at low overpotentials, but the implementation of inexpensive solar-driven water-splitting systems and electrolyzers could benefit from the development of robust, efficient, and abundant alternatives to noble metal catalysts. Transition metal phosphides (MxPy) have recently been identified as a promising family of Earth abundant electrocatalysts for the hydrogen-evolution reaction (HER) and are capable of operating with low overpotentials at operationally relevant current densities while exhibiting stability under strongly acidic conditions. In this review, we highlight the progress that has been made in this field and provide insights into the synthesis, characterization, and electrochemical behavior of transition metal phosphides as HER electrocatalysts. We also discuss strategies for the incorporation of metal phosphides into integrated solar-driven water-splitting systems and highlight key considerations involved in the testing and benchmarking of such devices. [ABSTRACT FROM AUTHOR]

Amorphous molybdenum phosphide (MoP)nanoparticles have been synthesizedand characterized as electrocatalysts for the hydrogen-evolution reaction(HER) in 0.50 M H2SO4(pH 0.3). Amorphous MoPnanoparticles (having diameters of 4.2 ± 0.5 nm) formed uponheating Mo(CO)6and trioctylphosphine in squalane at 320°C, and the nanoparticles remained amorphous after heating at450 °C in H2(5%)/Ar(95%) to remove the surface ligands.At mass loadings of 1 mg cm–2, MoP/Ti electrodesexhibited overpotentials of −90 and −105 mV (−110and −140 mV without iRcorrection) at currentdensities of −10 and −20 mA cm–2,respectively. These HER overpotentials remained nearly constant over500 cyclic voltammetric sweeps and 18 h of galvanostatic testing,indicating stability in acidic media under operating conditions. AmorphousMoP nanoparticles are therefore among the most active known molybdenum-basedHER systems and are part of a growing family of active, acid-stable,non-noble-metal HER catalysts. [ABSTRACT FROM AUTHOR]

Nanoparticles of nickel phosphide (Ni2P) have been investigated for electrocatalytic activity and stability for the hydrogen evolution reaction (HER) in acidic solutions, under which proton exchange membrane-based electrolysis is operational. The catalytically active Ni2P nanoparticles were hollow and faceted to expose a high density of the Ni2P(001) surface, which has previously been predicted based on theory to be an active HER catalyst. The Ni2P nanoparticles had among the highest HER activity of any non-noble metal electrocatalyst reported to date, producing H2(g) with nearly quantitative faradaic yield, while also affording stability in aqueous acidic media. [ABSTRACT FROM AUTHOR]

Review: 200 refs. [ABSTRACT FROM AUTHOR]