Phase Evolution of Vulcanized Co3O4 Catalysts during Oxygen Evolution Reaction

Abstract Transition metal-based sulfide catalysts for electrocatalytic oxygen evolution have been reported, but such sulfide catalysts are not stable under the condition of high overpotential and strong alkalinity used for oxygen evolution reaction. Herein, a series of vulcanized Co3O4 nanocubes with different vulcanization degree were synthesized. The optimized electrocatalyst delivered a lower overpotential of 314 mV at 10 mA cm-2 with a small Tafel slope of 67.4 mV dec-1 in 1 M KOH. The catalyst after long time of OER operation was then characterized and compared with the pristine catalyst. It was found that the precatalyst experienced in situ phase evolution with the generation of CoOOH species. On the catalytic electrode, the catalytic layer should be composed of vulcanized CoSx/ S-doped CoOOH that acts as catalytic active phase. This study provides new information for the sulfide electrocatalysts and is conducive to the design of advanced oxygen evolution catalysts.