Abstract
The hydrogen evolution reaction (HER) is a critical process in the electrolysis of water. Recently, much effort has been dedicated to developing low‐cost, highly efficient, and stable electrocatalysts. Transition metal phosphides are investigated intensively due to their high electronic conductivity and optimized absorption energy of intermediates in acid electrolytes. However, the low stability of metal phosphide materials in air and during electrocatalytic processes causes a decay of performance and hinders the discovery of specific active sites. The HER in alkaline media is more intricate, which requires further delicate design due to the Volmer steps. In this work, phosphorus‐modified monoclinic β‐CoMoO4 is developed as a low‐cost, efficient, and stable HER electrocatalyst for the electrolysis of water in alkaline media. The optimized catalyst shows a small overpotential of 94 mV to reach a current density of 10 mA cm−2 for the HER with high stability in KOH electrolyte, and an overpotential of 197 mV to reach a current density of 100 mA cm−2. Combined computational and in situ spectroscopic techniques show P is present as a surface phosphate ion; that electron holes localize on the surface ions and both (P—O1−) and Co3+—OH− are prospective surface active sites for the HER.
Highlights
The hydrogen evolution reaction (HER) is a critical process in the electrolysis straight-forward way to produce hydrogen at large-scale and would allow the use of water
Combined computational and in situ spectroscopic techniques show P is present as a surface phosphate ion; that electron holes localize on the surface ions and both (P–O1−) and Co3+–OH− are prospective surface monometallic and bimetallic compounds, such as oxides,[9] carbides,[10] nitrides,[11] sulfides,[12] and phosphides[13] have been explored as alternative HER electrocataactive sites for the HER
A series of P-doped CoMoO4 nanostructures on Ni foam were successfully synthesized by facile hydrothermalannealing
Summary
The higher frequency mode at 1392 cm−1 is not usually observed in phosphate minerals, but is present in phosphate glasses, where it is assigned to the stretching of terminal P O groups This analysis indicates that P exists as a phosphate group, in agreement with XPS results, and that it is under-coordinated such as would be the case for surface exposed PO43− groups identified in the computational work.[39] In addition, the fact that the P O contribution changes as a function of the applied voltage confirms it is active in the HER mechanism. These results suggest that the replacement of P to Mo is beneficial to the HER process by creating highly reactive surface active sites
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