In situ grown Co3O4/Co(OH)2 hybrids as efficient electrocatalysts for water oxidation

Abstract

Transition-metal oxides have been considered as water oxidation catalyst (WOC) alternatives to precious metal-based catalysts, but they generally display inferior electrocatalytic efficiency. A novel heterogeneous Co₃O₄/Co(OH)₂ hybrid is synthesized through a simple facile one-pot hydrothermal reaction. The as-obtained hierarchical Co₃O₄/Co(OH)₂ hybrids can serve as highly efficient electrocatalytic water oxidation catalysts for alkaline electrolytes. The prepared hierarchical Co₃O₄/Co(OH)₂ hybrids show strong interaction effects, facilitating the increase of the number of active sites and facile charge transfer ability. Remarkably, hierarchical Co₃O₄/Co(OH)₂ hybrids afforded electrocatalytic water oxidation activity, it requires a low potential of 1.60 V to obtain a current density of 10 mA cm⁻² and a small Tafel slope of approximately 103 mV dec⁻¹. A preliminary electrocatalytic water oxidation reaction mechanism catalyzed by a cobalt-based catalyst is proposed according to the reported publications and experimental data. The final step for oxygen evolution is the rate-determining step, which is supported by electrochemical experiments. This study indicates that the hierarchical Co₃O₄/Co(OH)₂ hybrids are promising as efficient electrocatalysts for water oxidation that can be used in water splitting for hydrogen production and generation of hydrocarbon fuels and fuel cells.