Ni–Mo Nanopowders for Efficient Electrochemical Hydrogen Evolution

Abstract

Earth-abundant metals are attractive alternatives to the noble metal composite catalysts that are used in water electrolyzers based on proton-exchange membrane technology. Ni−Mo alloys have been previously developed for the hydrogen evolution reaction (HER), but synthesis methods to date have been limited to formation of catalyst coatings directly on a substrate. We report a method 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 alkaline conditions approaches that of the most active reported non-noble HER catalysts, and the coatings display good stability under alkaline conditions. We have also estimated turnover frequencies per surface atom at various overpotentials and conclude 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.

Functional integration of Ni–Mo electrocatalysts with Si microwire array photocathodes to simultaneously achieve high fill factors and light-limited photocurrent densities for solar-driven hydrogen evolution

“…Ni-Mo nanopowder was synthesized following a previously reported procedure. 5 A Ni-Mo catalyst supported on carbon (Ni-Mo/C) was synthesized similarly to the Ni-Mo nanopowder except for use of an additional step that involved thoroughly grinding the Ni-Mo oxide with carbon black to form the supported structure. TiO 2 and Ni-Mo nanopowders were suspended in isopropanol at concentrations of 100 mg mL À1 and 1-2 mg mL À1 , respectively.…”

“…5 The device stability is not expected to be limited by Si or TiO 2 , as both materials are chemically stable under the operating conditions. Fig.…”

“…1,11 Alternatively, in photoelectrode structures comprised of a single photoabsorber, a transparent back contact can be used in conjunction with ''backside'' illumination so that the catalyst layer is not in the optical path of the semiconductor. [5][6][7]12 For integrated photoelectrodes in which the interfacial reactions can be performed by photogenerated minority carriers (as well as by majority carriers, for structures that contain a buried junction [8][9][10] ), the thickness of the electrocatalyst film can be adjusted to obtain an optimum compromise between the optical density and activity of the electrocatalyst film. This type of optimization favors the use of an extremely thin (o5 nm) catalytic layer, at the expense of catalytic activity.…”

Electrocatalysts for hydrogen oxidation and evolution reactions

“…Mo itself is not active for the HER. A NiMo alloy was found to be highly active in acid, but was not stable [84]. Recent research has focused on molybdenum compounds that are stable in acid.…”

Bottom-up Synthesis of Porous NiMo Alloy for Hydrogen Evolution Reaction

“…One of the most attractive porous metals is NiMo alloy which is known as one of the best hydrogen evolution electrode catalyst for cost-effective and highly efficient hydrogen production in water electrolysis [13,14]. Although different kinds of NiMo alloy porous morphologies were investigated such as HER catalysts including Ni 4 Mo [15], NiMo nanopowder [16], NiMo nanowire [17], the performances show that HER performance is not very enhanced due to the absence of bicontinuous and monolithic porous structures. Indeed, the Ni foam supported Ni 4 Mo nanoparticles, and the three-dimensional NiMo nanowires significantly improved their HER activities.…”