Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 25: Metal substrates: Adsorption of organic / bio molecules III
O 25.9: Vortrag
Dienstag, 23. März 2010, 12:30–12:45, H36
Joint experimental and theoretical studies of complex adsorption structures: Adsorption versus Interaction Strength — •J. Haubrich1, D. Loffreda2, F. Delbecq2, P. Sautet2, Y. Jugnet3, C. Becker1, and K. Wandelt1 — 1Inst. f. Phys. und Theo. Chemie, Universitaet Bonn — 2Lab. de Chimie, Ecole Normale Superieure de Lyon, France — 3Inst. de Rech. sur la Catalyse et Env., Villeurbanne, France
Model catalysis studies in UHV represent a crucial strategy to identify surface species, reaction mechanisms, and separate the roles of the catalysts, promoters and supports in heterogeneous catalysis. Combining powerful experimental tools with theoretical methods, surface processes can be studied nowadays in atomic level detail. Here we present a combined HREELS and DFT study of the adsorption and interaction of multifunctional molecules, crotonaldehyde and prenal, on Pt(111) and two Pt-Sn surface alloys. The identification of adsorption structures is a fundamental step towards understanding of the molecule-surface bonding and the reaction mechanisms in the selective hydrogenation of α,β-unsaturated aldehydes. We identified the stable adsorption structures on the three model surfaces and surprisingly find that the tin-induced changes in the vibrational properties disagree with the electronic modifications of the surfaces and the adsorption energies. Our detailed energetic analysis of the molecule-surface bonding reveals that the interaction energies of complex molecules with the substrate are very different than the adsorption energies and allow us to rationalize the vibrational frequencies.