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

The requirement of hydrogen adsorption free Gibbs energy (ΔGH*) 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 the effective strategy to obtain the optimal ΔGH*. Ni3N exhibits poor HER activity due to its undesirable ΔGH*. 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/cm2 and superior activity than benchmark Pt/C catalyst when the current density is greater than 125 mA/cm2. 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 obtains the optimal GH* and water adsorption energy.