Tracking Water Dissociation on RuO<sub>2</sub>(110) Using Atomic Force Microscopy and First-Principles Simulations
Austin Jerad Reese, Simon Gelin, Maria Maalouf, Neha Wadehra, Lei Zhang, Geoffroy Hautier, Darrell G. Schlom, Ismaïla Dabo, Jin Suntivich
Abstract
The interaction between interfacial water and transition metal oxides is a primary enabling step for the oxygen evolution reaction (OER). RuO 2 is a prototypical OER electrocatalyst whose ability to activate interfacial water molecules is essential to its OER activity. We image the dissociation of surface water into OH* and O* on RuO 2 (110), where * denotes adsorbed species, using atomic force microscopy. Starting from the surface-bound water molecules, which form a one-dimensional network along the rows of Ru surface sites, increasing the oxidative potential strips hydrogen away and transforms the water molecules into OH* and O*. This oxidative step changes the pattern of the adsorbates from one- to two-dimensional. First-principles calculations with interfacial polarization, capacitive charging, and adsorbate interactions attribute this evolution to the cooperative dehydrogenation of adsorbed water and OH* on RuO 2 . We use these results to map the surface phase diagram of RuO 2 (110) and provide a quantitative interpretation of its cyclic voltammetry. Our result provides the visualization of the water dissociation on a conductive oxide surface, a critical step in the OER, and demonstrates that the water activation is a collective phenomenon at RuO 2 (110) electrodes.