Gradient oxygen vacancy engineering of RuO2−x for efficient acidic water oxidation†

As the most active catalyst material in acidic environments, the catalytic activity of RuO₂ is higher than that of IrO₂, but poor stability limits its application. To this end, we propose a simple defect engineering strategy, namely the preparation of RuO₂ nanoparticles (D-RuO₂) with gradient distribution of oxygen vacancies as efficient acidic oxygen evolution reaction (OER) catalysts. Oxygen vacancies (V_O) participate in lattice compression to form an unsaturated coordination environment, which decreases the covalency of Ru–O bonds, effectively optimizes the adsorption of intermediates in the OER process, and stabilizes the structure of the active site. Density functional theory (DFT) calculations show that the presence of V_O shifts Ru's d band center closer to the Fermi level, which promotes the adsorption of oxygen-containing intermediates and accelerates the adsorbate evolution mechanism (AEM) process. D-RuO₂ exhibits a lower overpotential (η₁₀ = 197 mV) and a lower Tafel slope (58.67 mV dec⁻¹), with a stability of 60 h measured in 0.5 M H₂SO₄. This strategy provides a simple method to improve the activity and stability of RuO₂ by regulating oxygen vacancies.