Controllable modulation of the coordination environment of Ni atoms via vanadium doping to improve the water and hydrogen binding capability of NiO for low-overpotential alkaline hydrogen evolution

Nickel-based catalysts, especially NiO, have attracted great attention in alkaline hydrogen evolution reaction (HER) due to their abundant resources and controllable structures. However, the inherent high overpotential and lack of water dissociation sites of NiO limit its efficiency, which is a critical issue that needs to be addressed. In this study, we employed a strategy of modulating metal coordination bonds to enhance the HER performance of NiO. It is observed that Ni atoms in NiO transform from a six-coordinate structure to a mixed structure of three- and four-coordinate with appropriate V doping concentration, enhancing the charge density of Ni atoms, adjusting the Ni 3d orbitals, and reduces the crystal stabilization energy to −526.84 eV. The synthesized V-NiO-1-4 exhibits an overpotential of 38 mV at 10 mA cm−2, comparable to the benchmark Pt/C catalyst. Density functional theory (DFT) calculations and experimental reveal that V doping not only provides efficient water adsorption sites for NiO, reducing the energy barrier for H-OH bond cleavage to 0.24 eV, but also improves the hydrogen binding capability of Ni atoms, thereby accelerating the kinetics of alkaline Volmer and Heyrovsky reactions. This work provides a new concept and guidance for controllable design of efficient NiO electrodes for water electrolysis.