title: Reactivity of atomically dispersed Pt(2+) species towards H2: model Pt-CeO2 fuel cell catalyst.
abstract: The reactivity of atomically dispersed Pt(2+) species on the surface of nanostructured CeO2 films and the mechanism of H2 activation on these sites have been investigated by means of synchrotron radiation photoelectron spectroscopy and resonant photoemission spectroscopy in combination with density functional calculations. Isolated Pt(2+) sites are found to be inactive towards H2 dissociation due to high activation energy required for H-H bond scission. Trace amounts of metallic Pt are necessary to initiate H2 dissociation on Pt-CeO2 films. H2 dissociation triggers the reduction of Ce(4+) cations which, in turn, is coupled with the reduction of Pt(2+) species. The mechanism of Pt(2+) reduction involves reverse oxygen spillover and formation of oxygen vacancies on Pt-CeO2 films. Our calculations suggest the existence of a threshold concentration of oxygen vacancies associated with the onset of Pt(2+) reduction.
authors.affiliation: Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany. yaroslava.lykhach@fau.de.
authors.forename: Yaroslava
authors.initials: Y
authors.lastname: Lykhach
authors.affiliation: Departament de Química Física and Institut de Quimica Teòrica i Computacional (IQTCUB), Universitat de Barcelona, c/Martí Franquès 1, 08028 Barcelona, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Figueroba
authors.affiliation: CNR-IOM DEMOCRITOS, Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche and SISSA, Via Bonomea 265, I-34136, Trieste, Italy.
authors.forename: Matteo Farnesi
authors.initials: MF
authors.lastname: Camellone
authors.affiliation: Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany. yaroslava.lykhach@fau.de.
authors.forename: Armin
authors.initials: A
authors.lastname: Neitzel
authors.affiliation: Charles University, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, V Holešovičkách 2, 18000 Prague, Czech Republic.
authors.forename: Tomáš
authors.initials: T
authors.lastname: Skála
authors.affiliation: CNR-IOM DEMOCRITOS, Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche and SISSA, Via Bonomea 265, I-34136, Trieste, Italy.
authors.forename: Fabio R
authors.initials: FR
authors.lastname: Negreiros
authors.affiliation: Charles University, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, V Holešovičkách 2, 18000 Prague, Czech Republic.
authors.forename: Mykhailo
authors.initials: M
authors.lastname: Vorokhta
authors.affiliation: Charles University, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, V Holešovičkách 2, 18000 Prague, Czech Republic.
authors.forename: Nataliya
authors.initials: N
authors.lastname: Tsud
authors.affiliation: Elettra-Sincrotrone Trieste SCpA, Strada Statale 14, km 163.5, 34149 Basovizza-Trieste, Italy and IOM, Strada Statale 14, km 163.5, 34149 Basovizza-Trieste, Italy.
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Prince
authors.affiliation: CNR-IOM DEMOCRITOS, Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche and SISSA, Via Bonomea 265, I-34136, Trieste, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Fabris
authors.affiliation: Departament de Química Física and Institut de Quimica Teòrica i Computacional (IQTCUB), Universitat de Barcelona, c/Martí Franquès 1, 08028 Barcelona, Spain and Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain.
authors.forename: Konstantin M
authors.initials: KM
authors.lastname: Neyman
authors.affiliation: Charles University, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, V Holešovičkách 2, 18000 Prague, Czech Republic.
authors.forename: Vladimír
authors.initials: V
authors.lastname: Matolín
authors.affiliation: Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany. yaroslava.lykhach@fau.de and Erlangen Catalysis Resource Center, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Libuda