First-Principles Simulations of Water Dissociation on RuO₂(110)

The oxygen evolution reaction (OER) is a catalytic process pivotal to electrolysis and photosynthesis, whose kinetic rate correlates strongly with the ability of the catalyst to activate interfacial water molecules. To predict the dissociation of surface water into OH* and O* at the surface sites * of the prototypical RuO₂(110) electrocatalyst, we develop and apply a voltage-dependent model of the solvated surface. In the presence of surface-bound water molecules, increasing the oxidative potential strips hydrogen away following two spatially correlated desorption steps: a sequence of dehydrogenation events that transforms the water molecules into an array of alternating OHH* and OH* species and the subsequent sudden desorption of all protons. First-principles calculations with interfacial polarization, capacitive charging, and adsorbate interactions attribute this evolution to the cooperative dehydrogenation of OHH* and OH* on RuO₂. We use these results to map the surface phase diagram of RuO₂(110) and provide a quantitative interpretation of its cyclic voltammetry. Our results offer atomistic insights into water dissociation on conductive oxide surfaces, which is a critical step in the OER, and demonstrate that water activation at RuO₂ is a collective interfacial phenomenon.