RuO2 has a wide range of applications in photocatalytic water splitting, heterogeneous catalysis, electrochemistry and many other energy-related areas. Here, we prepared stoichiometric, reduced and oxidized RuO2(110) surfaces and studied water adsorption, dissociation, and diffusion using time-lapsed scanning tunneling microscopy. On stoichiometric RuO2(110) we show that water monomers adsorb on top of the Ru sites and are immobile below ~223 K. At temperatures above 238 K, the monomers are found to diffuse along Ru rows and form water dimers, trimers and tetramers with dimers being the most stable configuration. The onset for dimer diffusion is observed at ~ 277 K indicating higher diffusion barrier than that for monomers. The diffusion barrier for water dimers is determined to be ~0.73 eV, which is significantly higher compared to 0.35 eV determined previously on the isostructural TiO2 (110).1 On reduced RuO2(110), we find that water molecules dissociate in bridging oxygen vacancies forming pairs of bridging hydroxyls. Subsequently, both the along- and across-row diffusion of proton is observed at room temperature. On oxidized RuO2(110), water molecules react with oxygen adatoms on Ru rows and form pairs of terminal hydroxyl groups that can reversibly dissociate back to water and adatom. Along- and across-row diffusion of water molecules at room temperature is tracked by following the position of hydroxyl pairs.1 J. Matthiesen, J. Hansen, S. Wendt, E. Lira, R. Schaub, E. L�gsgaard, F. Besenbacher, and B. Hammer, Phys. Rev. Lett. 102 , 226101 (2009).

Imaging the dynamics of water molecules on RuO<sub>2</sub>(110)

248th National Meeting (2014)

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Imaging the dynamics of water molecules on RuO2(110)

Imaging the dynamics of water molecules on RuO₂(110)