Exploring efficient and economical electrocatalysts for hydrogen evolution reaction is of great significance for water splitting on an industrial scale. Tungsten oxide, WO, has been long expected to be a promising non-precious-metal electrocatalyst for hydrogen production. However, the poor intrinsic activity of this material hampers its development. Herein, we design a highly efficient hydrogen evolution electrocatalyst via introducing oxygen vacancies into WO nanosheets. Our first-principles calculations demonstrate that the gap states introduced by O vacancies make WO act as a degenerate semiconductor with high conductivity and desirable hydrogen adsorption free energy. Experimentally, we prepared WO nanosheets rich in oxygen vacancies via a liquid exfoliation, which indeed exhibits the typical character of a degenerate semiconductor. When evaluated by hydrogen evolution, the nanosheets display superior performance with a small overpotential of 38 mV at 10 mA cm and a low Tafel slope of 38 mV dec. This work opens an effective route to develop conductive tungsten oxide as a potential alternative to the state-of-the-art platinum for hydrogen evolution.
Developing bifunctional catalysts for both hydrogen and oxygen evolution reactions is apromising approach to the practical implementation of electrocatalytic water splitting. However,m ost of the reported bifunctional catalysts are only applicable to alkaline electrolyzer,although afew are effective in acidic or neutral media that appeals more to industrial applications.H ere,alithium-intercalated iridium diselenide (Li-IrSe 2 )i sd eveloped that outperformed other reported catalysts towardo verall water splitting in both acidic and neutral environments.L ii ntercalation activated the inert pristine IrSe 2 via bringing high porosities and abundant Se vacancies for efficient hydrogen and oxygen evolution reactions.When Li-IrSe 2 was assembled into two-electrode electrolyzers for overall water splitting,t he cell voltages at 10 mA cm À2 were 1.44 and 1.50 Vu nder pH 0a nd 7, respectively,b eing record-low values in both conditions.
The two-dimensional surface or one-dimensional interface of heterogeneous catalysts is essential to determine the adsorption strengths and configurations of the reaction intermediates for desired activities. Recently, the development of single-atom catalysts has enabled an atomic-level understanding of catalytic processes. However, it remains obscure whether the conventional concept and mechanism of one-dimensional interface are applicable to zero-dimensional single atoms. In this work, we arranged the locations of single atoms to explore their interfacial interactions for improved oxygen evolution. When iridium single atoms were confined into the lattice of CoOOH, efficient electron transfer between Ir and Co tuned the adsorption strength of oxygenated intermediates. In contrast, atomic iridium species anchored on the surface of CoOOH induced inappreciable modification in electronic structures, whereas steric interactions with key intermediates at its Ir−OH−Co interface played a primary role in reducing its energy barrier toward oxygen evolution.
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