VS: an efficient catalyst for an electrochemical hydrogen evolution reaction in an acidic medium.

In view of preparing efficient electrocatalysts for energy conversion applications, we have developed an eco-friendly, cost effective, single step method for the scalable synthesis of VS2 and its reduced graphene oxide composite VS4/rGO. Furthermore, the electrocatalytic performances of the catalysts have been studied toward the hydrogen evolution reaction in an acid medium (0.1 M H2SO4). Presumably, the large exposed electrochemical active surface area (27.7 cm2) and hexagonal crystal lattice of VS2 result in its dominating catalytic performance over that of the linear VS4/rGO composite. Also, a VS2 modified electrode was demonstrated to have better stability (with a negligible change in the overpotential even after 10 h and 43 h of continuous electrolysis) with a notably low Tafel slope (36 mV dec-1, close to that of commercial Pt/C) and onset potential (15 mV vs. RHE) with robust durability for long term application. A preliminary study on the photoelectrochemical activities of VS2 showed a significant decrease in the charge transfer resistance upon illumination of light on the electrode surface.