Enhanced OER Performances of Au@NiCo₂S₄ 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@NiCo₂S₄ core-shell heterostructure nanoparticles (NPs) and bare NiCo₂S₄ NPs were prepared. The measurement of the OER catalytic performance showed that the catalytic activity of Au@NiCo₂S₄ core-shell heterostructure was enhanced compared to bare NiCo₂S₄ NPs. At the current density of 10 mA cm^-2, the overpotential of Au@NiCo₂S₄ (299 mV) is lower than that of bare NiCo₂S₄ (312 mV). The Tafel slope of Au@NiCo₂S₄ (44.5 mV dec^-1) was reduced compared to that of bare NiCo₂S₄ (49.1 mV dec^-1), 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@NiCo₂S₄ 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.