title: Dissociation of water on oxygen-covered Rh{111}.
abstract: The adsorption of water and coadsorption with oxygen on Rh{111} under ultrahigh vacuum conditions was studied using synchrotron-based photoemission and photoabsorption spectroscopy. Water adsorbs intact on the clean surface at temperatures below 154 K. Irradiation with x-rays, however, induces fast dissociation and the formation of a mixed OH+H(2)O layer indicating that the partially dissociated layer is thermodynamically more stable. Coadsorption of water and oxygen at a coverage below 0.3 monolayers has a similar effect, leading to the formation of a hydrogen-bonded network of water and hydroxyl molecules at a ratio of 3:2. The partially dissociated layers are more stable than chemisorbed intact water with the maximum desorption temperatures up to 30 K higher. For higher oxygen coverage, up to 0.5 monolayers, water does not dissociate and an intact water species is observed above 160 K, which is characterized by an O 1s binding energy 0.6 eV higher than that of chemisorbed water and a high desorption temperature similar to the partially dissociated layer. The extra stabilization is most likely due to hydrogen bonds with atomic oxygen.
authors.affiliation: Department of Chemistry, The University of Reading, Whiteknights, Reading RG6 6AD, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Shavorskiy
authors.forename: T
authors.initials: T
authors.lastname: Eralp
authors.forename: E
authors.initials: E
authors.lastname: Ataman
authors.forename: C
authors.initials: C
authors.lastname: Isvoranu
authors.forename: J
authors.initials: J
authors.lastname: Schnadt
authors.forename: J N
authors.initials: JN
authors.lastname: Andersen
authors.forename: G
authors.initials: G
authors.lastname: Held