Plasma-induced vacancies in CoS2 electrocatalysts to activate sulfur sites for hydrogen evolution reaction

Exploring efficient non-precious metal sulfides as electrocatalysts for the hydrogen evolution reaction (HER) is crucial. Cobalt disulfide (CoS 2 ) has gained attention for its favorable intrinsic activity, impressive metal conductivity, and cost-effectiveness. However, the weak adsorption of H* at the sulfur (S) sites on the surface of CoS 2 leaves room for enhancing its HER intrinsic activity. Vacancy engineering emerges as a valuable strategy to modulate the local charge density, optimizing hydrogen adsorption free energy and catalytic performance in HER. Taking advantage of plasma technology , known for its rapid and efficient defect creation, we synthesized porous CoS 2 nanowire arrays enriched with S vacancies (V s -CoS 2 /CC) through Ar plasma treatment . Notably, at a current density of 10 mA cm −2 , V s -CoS 2 /CC exhibits a lower overpotential (170 mV) compared to pure CoS 2 /CC (236 mV). Furthermore, V s -CoS 2 /CC demonstrates exceptional electrochemical stability. Experimental data and density functional theory calculations jointly reveal that introducing S vacancies reduces local charge density around S atoms, activating inert sulfur sites and enhancing the intrinsic activity of CoS 2 for HER. This study introduces a novel concept of defect-engineered activation in metal compound catalysts, employing a plasma approach to advance HER performance.