Suppressing the aggregation and optimizing the electronic structure of porous Ni nanosheets by POMs-derived Mo₂N for efficient hydrogen evolution in AEM water electrolysis

NiMo-based catalysts show significant potential for the hydrogen evolution reaction (HER). Optimizing the electronic structure and enhancing mass transfer are two critical factors for improving catalytic performance, but they remain significant challenges. Herein, we present a route for synthesizing two-dimensional (2D) porous Mo2N-Ni heterojunction nanosheets with tuned Ni-Mo ratio for enhanced alkaline HER performance. A precursor can be easily synthesized by assembling polyoxometalate clusters (PMo12) with layered hydroxy oxides (Ni(OH)2). It is found that the interaction between PMo12 and Ni(OH)2 can effectively protect the particles from significant agglomeration during pyrolysis, resulting in the formation of 2D porous sheets composed of small Mo2N-Ni units. The transfer of electrons from Ni to Mo2N results in the redistribution of electrons at the heterojunction, optimizing the adsorption and desorption of intermediates. Moreover, the 2D porous structure comprised of small particles enhances mass transfer, thereby reducing the impedance of the catalyst. Consequently, the catalyst with an optimized Mo/Ni ratio exhibits an overpotential of 19 mV at 10 mA cm−2, being comparable to that of commercial Pt/C catalyst. The anion exchange membrane (AEM) electrolyzer, consisting of optimized Mo2N-Ni and NiFe-LDH, achieves a current density of 500 mA cm−2 at 1.80 V and can operate stably for 300 h. This assembly method offers an effective strategy for the large-scale preparation of efficient catalysts.