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

Abstract

Transition-metal sulfides (M_xS_y) 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 M_xS_y (S–H_ads) 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–H_ads 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.