Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 8: Surface Chemical Reactions and Heterogeneous Catalysis I
O 8.2: Vortrag
Montag, 11. März 2013, 10:45–11:00, H33
Adsorption and decomposition of acetic acid on ceria-based model catalysts — •A. Neitzel1, Y. Lykhach1, V. Johánek2, N. Tsud2, T. Skála3, K. C. Prince3, V. Matolín2, and J. Libuda1 — 1FAU Erlangen-Nürnberg, Germany — 2Charles University in Prague, Czech Republic — 3Sincrotron Trieste, Italy
The adsorption and decomposition of acetic acid on stoichiometric CeO2(111), partially reduced CeO2−x, and Pt/CeO2 thin films prepared on Cu(111) were investigated by synchrotron radiation and resonant photoelectron spectroscopy. Molecular acetic acid and acetate are the major species formed upon adsorption at 150 K. Decomposition of these species on CeO2(111) does not alter the oxidation state of cerium cations. In contrast, decomposition of acetic acid on CeO2−x results in re-oxidation between 250 and 400 K, followed by reduction of ceria and C-C bond cleavage above 400 K. Intermediate decomposition products like formate, alkoxy, and alkyl species were identified on the surface. These were converted into thermally stable carbonaceous species above 600 K. On Pt/CeO2, hydrogen spillover and reverse spillover were observed during annealing. Furthermore, CO, alkoxy, alkyl moieties, and elemental carbon were detected. Above 500 K, reverse oxygen spillover from ceria to Pt particles resulted in oxidative removal of carbonaceous species. It was found that C-C bond cleavage is promoted in presence of oxygen ad-atoms on Pt(111) and Pt/CeO2. As a result, formation of methoxy species and hydroxyl groups on Pt was observed. On Pt/CeO2, pre-exposed to oxygen, hydrogen reverse spillover was found to be suppressed.