In situ cathodic activation of V-incorporated Ni x S y nanowires for enhanced hydrogen evolution.

In situ cathodic activation (ISCA) of V-incorporated Nix Sy nanowires supported on nickel foam (VS/Nix Sy /NF) can be realized in an alkaline hydrogen evolution reaction (HER) process, which provides not only clearly enhanced activity but also ultrahigh stability for HER. The ISCA process is continuous linear sweep voltammetry (LSV) on VS/Nix Sy /NF as a cathodic electrode with gradually enhanced HER activity. The activated VS/Nix Sy /NF (A-VS/Nix Sy /NF) demonstrates enhanced HER activity with an overpotential of 125 mV to drive 10 mA cm-2 , which is much lower than that of other samples. It may be predicted that the ISCA-derived amorphous VOOH film covering on A-VS/Nix Sy /NF accelerates the HER process, and NiOOH may protect active sites from decaying, leading to excellent activity and structural stability. However, for single metal sulfides, the ISCA process of nickel or vanadium sulfides is not available, implying that the synergistic effect between Ni and V of VS/Nix Sy /NF may be the key to drive ISCA in alkaline HER. In addition, its ultra-high stability confirms that the stable active sites and nanostructures of A-VS/Nix Sy /NF are derived from ISCA. Therefore, the ISCA of V-incorporated transition metal sulfides in the alkaline HER process may be a facile and promising method to obtain efficient electrocatalysts.