F dopants triggered active sites in bifunctional cobalt sulfide@nickel foam toward electrocatalytic overall water splitting in neutral and alkaline media: Experiments and theoretical calculations

As a member of the transition metal sulfide family, cobalt sulfides (CoS x ) are considered as highly-activity, cost-effectively, as well as stable electrocatalysts with huge potential for the application of water splitting. Combining experiments and theoretical calculations, we demonstrated that F dopants could activate the Co and S sites of CoS 2 in CoS 2 @NF composites prepared via one-step hydrothermal method and contribute to enhance the intrinsic electrical conductivity, achieving a significantly improved activity of water splitting. The improved surface wettability in F-doped CoS 2 @NF composites ensures rapid electrolyte penetration and accelerates migration of hydroxyl as well as oxygen release. Furthermore, the F-doped CoS 2 @NF composites exhibit remarkable electrocatalytic activity and excellent long-term operational stability for overall water splitting in alkaline and neutral media. Predominantly, our work could be explored to enhance and understand the catalytic properties of other transition metal sulfides, and be also expected for further progress achieved with other nonmetal element dopants.