v-NiS/NiS Heterostructures Achieving Ultralow Overpotential in Alkaline Hydrogen Evolution.

The hydrogen evolution reaction (HER) usually has slow kinetics in an alkaline environment because of the lack of binding protons. Herein, we use a simple strategy to prepare NiS/NiS heterostructure (HS) electrocatalysts rich in sulfur vacancies (v). The v-NiS/NiS HSs demonstrate an ultralow overpotential of 44 mV at the current density of 10 mA cm and corresponding Tafel slope of 42 mV dec. The improved activity and accelerated reaction kinetics of v-NiS/NiS HSs are derived from the dual regulation of morphology engineering and defect engineering, which not only increases the number and exposure of active sites but also optimizes the adsorption of active sites and active species. This work provides a potential non-noble metal candidate for efficient hydrogen evolution in an alkaline environment and a feasible method for constructing a high-performance electrocatalyst.