Surface structure evolution of bimetallic nickel tungsten nitride (Ni2W3N) for high performance hydrogen evolution

초록

Bimetallic transition metal nitride (TMN)-based electrocatalysts have demonstrated potential for the hydrogen evolution reaction (HER) in alkaline electrolytes. However, achieving simpler synthesis methods and a deeper understanding of their catalytic activity remains challenging. Here, we report a facile synthesis strategy for Ni2W3N directly on nickel foam (Ni2W3N/NF). Unlike conventional methods for synthesizing bimetallic TMN-based catalysts requiring two-step annealing, our approach streamlines the annealing process into a one-step. It also eliminates the use of toxic NH3 gas and additional Ni precursors. Notably, this work is the first to report Ni2W3N/NF as an HER catalyst. The resulting Ni2W3N/NF exhibits one of the best HER performances among bimetallic TMN-based catalysts, with low overpotential values of 46.5 and 78.7 mV at current densities of 50 and 100 mA cm-2, respectively, and demonstrates high stability for 72 h. In situ Raman spectroscopy reveals surface reconstruction during the HER process, characterized by tungsten dissolution and the formation of amorphous Ni(OH)2. Density functional theory calculations indicate that the Ni sites in amorphous Ni(OH)2 serve as active sites, enhancing water dissociation and optimizing hydrogen binding energy. This facilitates an efficient Volmer reaction, thereby improving HER performance.

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