Nb2O5–Ni3N heterojunction tuned by interface oxygen vacancy engineering for the enhancement of electrocatalytic hydrogen evolution activity

Abstract

The requirement of hydrogen adsorption Gibbs free energy (ΔG_H*) approximating to 0 eV limits the hydrogen evolution reaction (HER) activity of most electrocatalysts in alkaline media. The construction of interface and defects engineering is an effective strategy to obtain the optimal ΔG_H*. Ni₃N exhibits poor HER activity due to its undesirable ΔG_H*. By cooperating with Nb₂O₅, the d-band center of Ni₃N was reduced, improving its catalytic performance. The optimized Nb₂O₅–Ni₃N displays an overpotential of 80 mV at 10 mA cm⁻² and superior activity than the benchmark Pt/C catalyst when the current density is greater than 125 mA cm⁻². Experimental and density functional theory results demonstrate that the improved catalytic activity is because the electronic interaction between Ni and Nb changes the coordination numbers of these two atoms, resulting in oxygen vacancies at the interface. Under the synergistic effect of Nb₂O₅ and Ni₃N, the catalyst exhibits optimal ΔG_H* and water adsorption energy.