The rational design of Ni3S2 nanosheets–Ag nanorods on Ni foam with improved hydrogen adsorption sites for the hydrogen evolution reaction

Transition-metal sulfides (MxSy) have attracted great interest as promising catalysts for the hydrogen evolution reaction (HER) due to their low cost. However, the formation of sulfur–hydrogen bonds on MxSy (S–Hads) severely suppresses the HER. In this paper, we report a three-dimensional nickel sulfide (Ni3S2) film supported by Ag nanorods (NRs) on Ni foam (Ni3S2–Ag/NF) as a type of electrocatalyst for the HER in alkaline media. The tight coupling between Ag and Ni3S2 creates a mass of heterojunctions. Therefore, this electrocatalyst only shows a low overpotential of 161 mV at 10 mA cm−2, as well as satisfactory stability for 10 h. Density functional theory calculations reveal that the intense electronic interactions in the heterojunctions of the Ni3S2–Ag hybrids can facilitate water adsorption and activation, improve H-adsorption and desorption on the electrocatalysts, and reduce the formation of S–Hads bonds on the catalyst surfaces. The existence of strong interactions between Ag and Ni3S2 in the electrocatalyst can facilitate both the Volmer and Heyrovsky steps of the HER and cause the Ni3S2–Ag/NF electrocatalysts to exhibit outstanding HER catalytic performance. This suitable strategy involving Ag doping may be a promising choice for developing Ni sulfide-based electrocatalysts for the HER.