Synthesis of yolk–shell Co3O4/Co1−xRuxO2 microspheres featuring an enhanced electrocatalytic oxygen evolution activity in acidic medium

Abstract

Hollow structures made of nanoscale building blocks are of great interest as catalysts for electrochemical water splitting. Here we report a solution-phase synthesis of yolk–shell Co₃O₄/Co_1−xRu_xO₂ microspheres (MSs) having a shell made of Co_1−xRu_xO₂ nanorods and the core of Co₃O₄. Benefiting from the peculiar morphology and the synergy between the different materials present in the MSs, the latter exhibit enhanced electrochemical oxygen evolution activity and long-term stability in acidic media. The catalyst achieves a catalytic current density of 10 mA cm⁻² at an overpotential of only 240 mV, a small Tafel slope of 70 mV dec⁻¹, and a high mass activity of 600 A g⁻¹ and maintains its activity throughout a 24 h chronopotentiometry tests at constant current densities of 10 and 20 mA cm⁻².