Berlin 2008 – wissenschaftliches Programm

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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

Mittwoch, 27. Februar 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.