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O: Fachverband Oberflächenphysik

O 4: Heterogeneous catalysis I

O 4.3: Vortrag

Montag, 22. März 2010, 11:45–12:00, H33

Nanostructured Cerium Oxide Based Model Catalysts: Structure, Morphology and Reactivity — •Thorsten Staudt¹, Yaroslava Lykhach¹, Michael Peter Andreas Lorenz¹, Regine Streber¹, Lutz Hammer², Hans-Peter Steinrück¹, Alexander Schneider², and Jörg Libuda¹ — ¹Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen — ²Lehrstuhl für Festkörperphysik, Friedrich-Alexander-Universität Erlangen

Nanostructured cerium oxide based catalysts offer unique properties in the field of heterogeneous catalysis, e.g. involving the activation of CO₂. In our study we prepare model systems starting from CeO₂(111) films on a Cu(111) substrate. Ultra-thin films are grown by PVD in O₂ at different sample temperatures. The morphology is analyzed by STM and LEED [1], showing a (1.5x1.5) superstructure. STM reveals a 3d growth mode for films grown at elevated temperatures (520K). Using kinetically limited growth at 100K and subsequent annealing, closed layers of ceria with atomically flat terraces can be prepared, even in the ultra-thin regime (1.5 ML). Via homoepitaxial growth of ceria on this initial film, closed films with larger thickness (3 ML) are available.

In a second step, the ceria substrate is modified by deposition of MgO, which offers basic sites and may further enhance the reactivity. We have investigated the influence of surface structure, oxidation state and composition of these samples on their interaction with CO₂.[2] Systematic XPS studies show that two CO₂ related species are formed, which are assigned to carbonates and carboxylates. [1] T. Staudt et al., Surface Science 603 (2009) 3382 [2] Y. Lykhach et al., submitted