Metal-oxygen bonding characteristics dictate activity and stability differences of RuO₂ and IrO₂ in the acidic oxygen...

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 reveals that RuO₂ exhibits ionic-dominated metal-oxygen bonds with delocalized electron distribution, facilitating intermediate desorption but promoting detrimental RuO₄^2- 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 the bonding nature and electrocatalytic performance metrics, offering fundamental insights for the rational design of acid-stable OER electrocatalysts with optimized activity-stability relationships.