Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 86: Heterogeneous catalysis I
O 86.3: Vortrag
Donnerstag, 17. März 2011, 17:00–17:15, WIL B122
Role of Pt in SO2 storage over ceria-based traps — Markus Happel1, •Yaroslava Lykhach1, Natalia Tsud2, Tomáš Skála3, Kevin C. Prince3, Vladimír Matolín2, and Jörg Libuda1 — 1Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen — 2Department of Plasma and Surface Science, Charles University, CZ-18000 Prague 8 — 3Sincrotrone Trieste, I-34012 Basovizza-Trieste
CeO2 based materials are efficient SOx traps that can be used in combination with three-way catalytic converters and NOx storage and reduction catalysts. Pt significantly enhances the SOx storage capability. However, the mechanism of this enhancement is not fully clear. In order to explore the role of Pt, we have studied the adsorption of SO2 on single-crystal-based stoichiometric and reduced ceria films and on Pt/CeO2(111) model catalysts. Reaction and decomposition of SO2 were investigated by means of synchrotron radiation and resonant PES. We found that SO3 is the major product of SO2 reaction on the surfaces of both, stoichiometric and reduced ceria. On stoichiometric ceria, SO3 decomposition occurs by desorption of SO2. In contrast, we detect progressive decomposition of SO3 to SOx and S species on reduced ceria. This leads to partial reoxidation of ceria and formation of sulfides. On Pt/CeO2, formation of SO3 on the ceria surface is accompanied by partial decomposition of SO2 to atomic sulfur on the Pt surface. Further decomposition of SO3 proceeds via spillover of SOx species to Pt followed by decomposition to atomic sulfur. Spillover of atomic sulfur from Pt to CeO2 results in formation of cerium sulfides.