Promoting the water dissociation of nickel sulfide electrocatalyst through introducing cationic vacancies for accelerated hydrogen evolution kinetics in alkaline media

Developing cost-effective non-precious electrocatalysts with excellent HER performance in alkaline media is of significance for industrial hydrogen production. Herein, we successfully endow Ni3S2 with unprecedentedly enhanced alkaline HER activities by introducing nickel vacancies. The Ni3S2 catalyst with nickel vacancies exhibits an ultralow overpotential of 35 mV at 10 mA cm−2 in 1 M KOH electrolyte, outperforming commercial Pt/C (56 mV) and most reported non-precious electrocatalysts. The electron paramagnetic resonance and X-ray absorption fine structure etc. validates the formation of Ni vacancies and the change of the geometric/electronic structure of Ni3S2. Additionally, the theoretical calculations reveal that the Ni sites with higher valence state neighbouring the Ni vacancies can promote the water dissociation, playing a vital role in accelerating HER kinetics in alkaline media. This work may provide a universal strategy to enhance the HER activity of transition-metal compound catalysts in alkaline media by means of cationic defect engineering.