Ethanol Diffusion on Rutile TiO2(110) Mediated by H Adatoms

We have studied the diffusion of ethanol on rutile TiO2(110)-(1 × 1) by high-resolution scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations. Time-lapsed STM images recorded at ∼200 K revealed the diffusion of ethanol molecules both parallel and perpendicular to the rows of surface Ti atoms. The diffusion of ethanol molecules perpendicular to the rows of surface Ti atoms was found to be mediated by H adatoms in the rows of bridge-bonded O (Obr) atoms similarly to previous results obtained for water monomers. In contrast, the diffusion of H adatoms across the Ti rows, mediated by ethanol molecules, was observed only very rarely and exclusively on fully hydrogenated TiO2(110) surfaces. Possible reasons why the diffusion of H adatoms across the Ti rows mediated by ethanol molecules occurs less frequently than the cross-row diffusion of ethanol molecules mediated by H adatoms are discussed.