Quadruple perovskite ruthenate as a highly efficient catalyst for acidic water oxidation

Development of highly active and durable oxygen-evolving catalysts in acid media is a major challenge to design proton exchange membrane water electrolysis for producing hydrogen. Here, we report a quadruple perovskite oxide CaCu₃Ru₄O₁₂ as a superior catalyst for acidic water oxidation. This complex oxide exhibits an ultrasmall overpotential of 171 mV at 10 mA cm^-2_geo, which is much lower than that of the state-of-the-art RuO₂. Moreover, compared to RuO₂, CaCu₃Ru₄O₁₂ shows a significant increase in mass activity by more than two orders of magnitude and much better stability. Density functional theory calculations reveal that the quadruple perovskite catalyst has a lower Ru 4d-band center relative to RuO₂, which effectively optimizes the binding energy of oxygen intermediates and thereby enhances the catalytic activity.