Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 13: Heterogeneous Catalysis

O 13.4: Talk

Monday, February 25, 2008, 14:45–15:00, HE 101

Influence of the substrate on the catalytic activity of Au/TiO₂(110) model catalysts — •Stefan Kielbassa, Menhild Eyrich, Joachim Bansmann, and Rolf-Jürgen Behm — Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm, Germany

In recent years, oxide supported Au catalysts and, in particular, the low temperature CO oxidation have intensively been examined. However, various topics, like the influence of the support on the catalytic activity, are still controversially discussed. Here, we present results on the influence of the chemical nature of the TiO₂(110) support on the activity of Au/TiO₂(110) model catalysts. Substrates with different surface structures and (bulk) oxidation states were prepared by using different preparation cycles (such as annealing and sputtering steps). After deposition of Au nanoparticles by thermal evaporation (Θ = 0.5 ML), the activity of the model catalysts was examined in a micro-flow reactor. Samples with fully oxidized substrates are nearly catalytically inactive, while for catalysts based on bulk-reduced substrates or thin TiO₂ films, the activity is up to 50 times higher. Atomic force microscopy (AFM) images of the surfaces show that, on the bulk-reduced supports, Au particle densities and sizes do not differ significantly and thus cannot be made responsible for the observed variations in the activity. A high activity of oxygen surface vacancies is discussed as origin of the enhanced activity of these catalysts.