Metal–Organic-Framework-Derived Hollow CoSx@MoS2 Microcubes as Superior Bifunctional Electrocatalysts for Hydrogen Evolution and Oxygen Evolution Reactions

Electrocatalytic water-splitting catalysts play important roles in clean energy conversion systems. Herein, metal–organic framework-derived (MOF-derived) hollow CoSx@MoS2 microcubes were successfully synthesized by a novel method. Co-MOF [(CH3)2NH2][Co(HCOO)3] prepared by a simple liquid precipitation method at room temperature reacted with S2– released from thioacetamide (TAA) to generate Co9S8 under solvothermal conditions. Through hydrothermal treatment, numerous MoS2 nanosheets grew on the surface of CoSx vertically and uniformly after introduction of sulfur and molybdenum sources, finally generating CoSx@MoS2 heterostructures. As bifunctional electrocatalysts, the heterostructures exhibited remarkable performance for the hydrogen evolution reaction with a low overpotential of 239 mV when the current density increased up to 10 mA cm–2 and a small Tafel slope of 103 mV dec–1 in 0.5 M H2SO4. They also worked effectively for the oxygen evolution reaction with a low overpotential of 347 mV at 10 mA cm–2 in 1 M KOH. The enhanced electrocatalytic activities of CoSx@MoS2 can be ascribed to their unique heterostructures and the synergism between CoSx and MoS2.