Synthesis of Yolk-Shell Co3O4/Co1-xRuxO2 Microspheres Featuring an Enhanced Electrocatalytic Oxygen Evolution in Acidic Medium

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/Co1-xRuxO2 microspheres (MSs) having a shell made of Co1-xRuxO2 nanorods and the core of Co3O4. Benefiting from the peculiar morphology and from the synergy between the different materials present in the MSs, the latter exhibit enhanced electrochemical oxygen evolution activity and long-term stability in acid media. The catalyst achieves 10 mA cm-2 of catalytic current density at an overpotential of only 240 mV, a small Tafel slope of 70 mVdec−1, a high mass activity of 600 A g-1 and maintains its activity throughout the 24 h chronopotentiometry test at a constant current density of 10 mA cm-2.