Metal-oxygen bonding characteristics dictate activity and stability differences of RuO and IrO in the acidic oxygen evolution reaction.

Ruthenium dioxide (RuO) and iridium dioxide (IrO) 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 RuO and IrO in acidic media. Mechanistic analyses reveal that RuO follows the adsorbate evolution mechanism with superior activity (theoretical overpotential: 0.698 V 0.909 V for IrO), while IrO demonstrates enhanced stability due to a higher dissolution energy change (>2.9 eV -0.306 eV for RuO). Electronic structure analysis reveals that RuO exhibits ionic-dominated metal-oxygen bonds with delocalized electron distribution, facilitating intermediate desorption but promoting detrimental RuO dissolution. In contrast, IrO features covalent bonding characteristics with more electron filling in Ir-oxygen bonds (2.942 2.412 for RuO), 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.