Steering elementary steps towards advanced alkaline hydrogen evolution via a sweet marriage of O-defected NiO and Cu

Water adsorption/dissociation and hydrogen intermediates (H*) desorption are the two elementary steps for hydrogen evolution reaction (HER) kinetics. This study builds on the promising concept of planning each step simultaneously to optimize in a whole. Theoretical and experimental approaches are combined to design and synthesize nickel oxide with moderate oxygen vacancy (VO) coating copper nanowires, namely m-VO NiO/Cu, for excellent HER in alkali. The construction of VO expedites H2O adsorption and dissociation on NiO, thereby significantly increases H* coverage on the surface. Subsequently, the incorporation of Cu creates accessible H* adsorption sites by limited hydrogen spillover from NiO to Cu, thereby facilitates the desorption of the next hydrogen directly on NiO continuously. The sweet marriage of VO NiO and Cu endows the most promising alkaline HER performance of a 20 mV overpotential at 10 mA cm–2 with a Tafel slope of 39.9 mV dec–1. This work presents a fresh perspective on upgrading multi-step reaction kinetics and encourages further research on advanced earth-abundant catalysts.