Bi-cation incorporated Ni₃N nanosheets boost water dissociation kinetics for enhanced alkaline hydrogen evolution...

Nickel nitride (Ni₃N) is a promising electrocatalyst for the hydrogen evolution reaction (HER) owing to its excellent metallic features and has been demonstrated to exhibit considerable activity for water oxidation. However, its undesirable characteristics as an HER electrocatalyst due to its poor unfavourable d-band energy level significantly limit its water dissociation kinetics. Herein, the HER electrocatalytic activity of Ni₃N was prominently enhanced via the simultaneous incorporation of bi-cations (vanadium (V) and iron (Fe), denoted as V-Fe-Ni₃N). The optimized V-Fe-Ni₃N displays impressive performance with an overpotential of 69 mV at 10 mA cm^-2 and good stability in 1.0 M KOH, which is remarkably better than pristine Ni₃N, V-doped Ni₃N, and Fe-doped Ni₃N and considerably closer to a commercial Pt/C catalyst. Based on density functional theory (DFT) studies, V and Fe atoms not only serve as active sites for promoting water dissociation kinetics but also tune the electronic structure of Ni₃N to achieve optimized hydrogen adsorption capabilities. This work presents an inclusive understanding of the rational designing of high-performance transition metal nitride-based electrocatalysts for hydrogen production. Its electrocatalytic performance can be significantly enhanced by doping transition metal cations.