Enhanced OER Performances of Au@NiCoS Core-Shell Heterostructure.

Transition metal sulfides have attracted a lot of attention as potential oxygen evolution reaction (OER) catalysts. Bimetallic sulfide possesses superior physicochemical properties due to the synergistic effect between bimetallic cations. By introducing a metal-semiconductor interface, the physicochemical properties of transition metal sulfide can be further improved. Using the solvothermal method, Au@NiCoS core-shell heterostructure nanoparticles (NPs) and bare NiCoS NPs were prepared. The measurement of the OER catalytic performance showed that the catalytic activity of Au@NiCoS core-shell heterostructure was enhanced compared to bare NiCoS NPs. At the current density of 10 mA cm, the overpotential of Au@NiCoS (299 mV) is lower than that of bare NiCoS (312 mV). The Tafel slope of Au@NiCoS (44.5 mV dec) was reduced compared to that of bare NiCoS (49.1 mV dec), indicating its faster reaction kinetics. Detailed analysis of its electronic structure, chemical state, and electrochemical impedance indicates that the enhanced OER catalytic performances of bare Au@NiCoS core-shell NPs were a result of its increased proportion of high-valance Ni/Co cations, and its increased electronic conductivity. This work provides a feasible method to improve OER catalytic performance by constructing a metal-semiconductor core-shell heterostructure.