Effect of Cation and Anion Vacancies in Ruthenium Oxide on the Activity and Stability of Acidic Oxygen Evolution

Electrocatalysts capable of working efficiently in acidic media for the oxygen evolution reaction (OER) are highly demanded for the large-scale utilization of proton exchange membrane (PEM) water electrolysis. This study focuses on the design and fabrication of cation/oxygen vacancy-enriched RuO₂ catalysts to investigate the impact of defect types on the OER activity and stability of RuO₂. The comprehensive blend of experimental and theoretical approaches elucidates that the presence of Ru vacancies in Ru_1–xO₂ modulates the d-band center and optimizes the adsorption energy of the OER intermediates, thereby augmenting the intrinsic OER activity. Conversely, the presence of oxygen vacancies in RuO_2-x diminishes the strength of Ru–O bonds, suppressing the involvement of the lattice oxygen oxidation mechanism (LOM) and Ru dissolution, consequently enhancing long-term stability. Notably, Ru_1–xO₂ exhibits the lowest overpotential of 212 mV at 10 mA cm_geo^–2, while RuO_2–x demonstrates superior stability, enduring 400 h under 10 mA cm_geo^–2, surpassing many catalysts for acidic OER in the literature. Our findings demonstrate that defect engineering is a promising strategy to achieve electrocatalysts with super catalytic performance in acid media for water electrolysis.