Metal-Oxygen Bonding Characteristics Dictate Activity and Stability Differences of RuO2 and IrO2 in Acidic Oxygen Evolution Reaction

Ruthenium dioxide (RuO2) and iridium dioxide (IrO2) serve as benchmark electrocatalysts for the acidic oxygen evolution reaction (OER), yet their intrinsic activity-stability relationships remain elusive. Herein, we employ density functional theory (DFT) calculations to systematically investigate the origin of divergent OER catalytic behaviors between RuO2 and IrO2 in acidic media. Mechanistic analyses reveal that RuO2 follows the adsorbate evolution mechanism with superior activity (theoretical overpotential: 0.698 V vs. 0.909 V for IrO2), while IrO2 demonstrates enhanced stability due to a higher dissolution energy change (>2.9 eV vs. -0.306 eV for RuO2). Electronic structure analysis uncovers that RuO2 exhibits ionic-dominated metal-oxygen bonds with delocalized electron distribution, facilitating intermediate desorption but promoting detrimental RuO42–dissolution. In contrast, IrO2 features covalent bonding characteristics with more electron filling in Ir-oxygen bonds (2.942 vs. 2.412 for RuO2), thereby stabilizing surface intermediates against dissolution at the expense of higher OER barriers. This work establishes a clear correlation between bonding nature and electrocatalytic performance metrics, offering fundamental insights for the rational design of acid-stable OER electrocatalysts with optimized activity-stability relationships.