Generation of Ni3S2 nanorod arrays with high-density bridging S22− by introducing a small amount of Na3VO4·12H2O for superior hydrogen evolution reaction

Abstract

Bridging S₂²⁻ moieties have been demonstrated to be highly active sites existing in metal polysulfides for the hydrogen evolution reaction (HER), thus the incorporation of high-density bridging S₂²⁻ into a Ni₃S₂ material to improve its electrocatalytic HER performance is highly desirable and challenging. Herein, we report a novel Ni₃S₂ nanorod array decorated with (020)-oriented VS₄ nanocrystals grown on nickel foam (S_hig-NS-rod/NF) via a simple and facile solvothermal method. Results show that the in situ incorporation of VS₄ not only triggers the formation of such a nanorod array structure, but also contributes to the uniform grafting of high-density and high catalytically active bridging S₂²⁻ sites on the interface between Ni₃S₂ and VS₄ for enhanced HER activity, and also promotes the absorption ability of OH⁻ radicals and thus accelerates the HER Volmer step in alkaline media. As expected, the resultant S_hig-NS-rod/NF material exhibits impressive catalytic performance toward the HER, with a much lower overpotential of 137 mV at 10 mA cm⁻² and a long-term durability for at least 22 h, and is superior to Ni₃S₂ nanorod arrays with low-density bridging S₂²⁻ (S_low-NS-rod/NF) and NS-film/NF counterparts (without VS₄), even outperforming the NF-supported 20% Pt/C at a large current density of over 120 mA cm⁻². Our findings put forward fresh insight into the rational design of highly efficient electrocatalysts toward the HER for green hydrogen fuel production.