Berlin 2008 – scientific programme
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O: Fachverband Oberflächenphysik
O 55: Poster Session III - MA 141/144 (Methods: Atomic and Electronic Structure; Particles and Clusters; Heterogeneous Catalysis; Semiconductor Substrates: Epitaxy and Growth+Adsorption+Clean Surfaces+Solid-Liquid Interfaces; Oxides and Insulators: Solid-Liquid Interfaces+Epitaxy and Growth; Phase Transitions; Metal Substrates: Adsorption of Inorganic Molecules+Epitaxy and Growth; Surface Chemical Reactions; Bimetallic Nanosystems: Tuning Physical and Chemical Properties; Oxides and insulators: Adsorption; Organic, polymeric, biomolecular films; etc.)
O 55.20: Poster
Wednesday, February 27, 2008, 18:30–19:30, Poster F
Inverse Au/TiO2 model catalysts studied with in-situ high-pressure XPS — •Dumbuya Karifala, Lucasczyk Thomas, Schirmer Michael, Marbach Hubertus, Gottfried Michael, and Steinrück Hans-Peter — Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg
We have prepared and investigated planar inverse TiO2/Au model catalysts using XPS and SEM. In addition, we have studied the surface composition and the electronic structure in the presence of CO and O2 at pressures of up to 1 mbar using high-pressure XPS. The model systems have been prepared and characterized on a polycrystalline Au foil and on an Au(111) surface. Initially, we used a recipe reported by Biener et al.[1] and prepared the TiO2 clusters by vapor deposition of Ti on the Au surfaces at 300 K, followed by oxidation with O2 at 300 K and annealing at 600-900 K in vacuum. We found that part of the deposited Ti forms an Au-Ti alloy during this procedure. To prevent alloying, we have developed a modified procedure in which the TiO2 clusters are annealed in an O2 atmosphere. SEM images of the nanoparticles on Au foil show a particle size distribution in the 10 nm range for an initial Ti coverage of 0.25 ML. At high coverages, exposure to CO and O2 did not reveal significant changes in the oxidation states of either Au or Ti, probably because of a buried TiO2/Au interface. In contrast, at lower TiO2 coverages (initial Ti coverage 0.25 ML) and CO pressures above 0.1 mbar, the in-situ XP spectra show changes that are attributed to the interaction between CO and Ti. 1. Biener et al.