title: Water-mediated proton hopping on an iron oxide surface.
abstract: The diffusion of hydrogen atoms across solid oxide surfaces is often assumed to be accelerated by the presence of water molecules. Here we present a high-resolution, high-speed scanning tunneling microscopy (STM) study of the diffusion of H atoms on an FeO thin film. STM movies directly reveal a water-mediated hydrogen diffusion mechanism on the oxide surface at temperatures between 100 and 300 kelvin. Density functional theory calculations and isotope-exchange experiments confirm the STM observations, and a proton-transfer mechanism that proceeds via an H(3)O(+)-like transition state is revealed. This mechanism differs from that observed previously for rutile TiO(2)(110), where water dissociation is a key step in proton diffusion.
authors.affiliation: Interdisciplinary Nanoscience Center and Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark.
authors.forename: Lindsay R
authors.initials: LR
authors.lastname: Merte
authors.forename: Guowen
authors.initials: G
authors.lastname: Peng
authors.forename: Ralf
authors.initials: R
authors.lastname: Bechstein
authors.forename: Felix
authors.initials: F
authors.lastname: Rieboldt
authors.forename: Carrie A
authors.initials: CA
authors.lastname: Farberow
authors.forename: Lars C
authors.initials: LC
authors.lastname: Grabow
authors.forename: Wilhelmine
authors.initials: W
authors.lastname: Kudernatsch
authors.forename: Stefan
authors.initials: S
authors.lastname: Wendt
authors.forename: Erik
authors.initials: E
authors.lastname: Lægsgaard
authors.forename: Manos
authors.initials: M
authors.lastname: Mavrikakis
authors.forename: Flemming
authors.initials: F
authors.lastname: Besenbacher