Atomic-Scale View on the H₂O Formation Reaction from H₂ on O‑Rich RuO₂(110)

The H₂O formation reaction from H₂ on O-rich RuO₂(110) was studied by temperature-programmed desorption and reaction (TPD/TPR) and scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations. On the one hand, following H2 adsorption at 270 K, our TPD/TPR measurements reveal that the on-top O species (O_ot) enhances the sticking probability of H₂, thus facilitating the H₂ adsorption and dissociation on O-rich RuO₂(110). On the other hand, for low H₂ adsorption temperature (170 K), the limited mobility of H_ad species hinders H₂ adsorption at a high coverage of preadsorbed O_ot. To better understand the strong influence of the adsorption temperature and the interplay between coadsorbed species, we conducted DFT calculations and high-resolution STM measurements. Two distinct adsorbate configurations, H_ad–O_ot and O_ot–H_ad–O_ot, are identified by STM. Mechanisms and molecular models for H₂ dissociation and H_ad diffusion on O-rich RuO₂(110) are proposed

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 (O_br) 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