Formulating a heterolytic cleavage process of water on Ni3N nanosheets through single transition metal doping for ultra-efficient alkaline hydrogen evolution

Abstract

Surface regulating the electronic structure and d-band center of electrocatalysts is very much crucial to improving their alkaline hydrogen evolution reaction (HER) performance. Herein, we combined density functional theory (DFT) computations and experimental studies to prepare and study single transition metal-doped Ni₃N nanosheets combined on Ni foam (M-Ni₃N, M = V, Cr, Mn, W, Mo, Co and Fe) for ultra-efficient alkaline hydrogen evolution. Physicochemical characterization of as-synthesized M-Ni₃N demonstrated that the electrons transferred and aggregated on the catalyst surface, which resulted in their unique electronic structure and chemical composition. DFT computations demonstrated that down-shifting of the d-band center weakened the adsorption energy of hydrogen and transition metal doping directly facilitated the adsorption of H₂O on M sites (desorption of H on Ni sites) at the surface of M-Ni₃N. As a result, a heterolytic cleavage process of water on M-Ni₃N nanosheets was formulated, thus drastically boosting the alkaline HER. Specifically, as the best example, the fabricated V-doped Ni₃N catalyst exhibited remarkable alkaline HER performance with significantly low overpotential of only 15 mV at a current density of 10 mA cm⁻². The strategy exemplified in this work provides a useful way to rational design for highly efficient hydrogen evolution reaction electrocatalysts.