title: Water production reaction on Rh110.
abstract: By means of scanning tunneling microscopy and density functional theory calculations, we studied the water formation reaction on the Rh(110) surface when exposing the (2 x 1)p2mg-O structure to molecular hydrogen, characterizing each of the structures that form on the surface during the reaction. First the reaction propagates on the surface as a wave front, removing half of the initial oxygen atoms. The remaining 0.5 monolayers of O atoms rearrange in pairs, forming a c(2 x 4) structure. Second, as the reaction proceeds, areas of an intermediate structure with c(2 x 2) symmetry appear and grow at the expense of the c(2 x 4) phase, involving all the oxygen atoms present on the surface. Afterward, the c(2 x 2) islands shrink, indicating that complete hydrogenation occurs at their edges, leaving behind a clean rhodium substrate. Two possible models for the c(2 x 2) structure, where not only the arrangement but also the chemical identity is different, are given. The first one is a mixed H + O structure, while the second one resembles the half-dissociated water layer already proposed on other metal surfaces. In both models, the high local oxygen coverage is achieved by the formation of a hexagonal network of hydrogen bonds.
authors.affiliation: Physics Department and Center of Excellence for Nanostructured Materials, University of Trieste, I-34127 Trieste, Italy. africh@tasc.infm.it
authors.forename: Cristina
authors.initials: C
authors.lastname: Africh
authors.forename: Haiping
authors.initials: H
authors.lastname: Lin
authors.forename: Martina
authors.initials: M
authors.lastname: Corso
authors.forename: Friedrich
authors.initials: F
authors.lastname: Esch
authors.forename: Renzo
authors.initials: R
authors.lastname: Rosei
authors.forename: Werner A
authors.initials: WA
authors.lastname: Hofer
authors.forename: Giovanni
authors.initials: G
authors.lastname: Comelli