Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 42: Poster Session II (Nanostructures at surfaces: arrays; Nanostructures at surfaces: Dots, particles, clusters; Nanostructures at surfaces: Other; Nanostructures at surfaces: Wires, tubes; Metal substrates: Adsorption of O and/or H; Metal substrates: Clean surfaces; Metal substrates: Adsorption of organic/bio moledules; Metal substrates: Solid-liquid interfaces; Metal substrates: Adsorption of inorganic molecules; Metal substrates: Epitaxy and growth; Heterogeneous catalysis; Surface chemical reactions; Ab-initio approaches to excitations in condensed matter; Organic, polymeric, biomolecular films– also with adsorbates; Particles and clusters)
O 42.75: Poster
Mittwoch, 25. März 2009, 17:45–20:30, P2
Characterization and catalytic properties of bimetallic Au-Pd(111) surfaces — •Marco Moors1, Tomasz Kobiela2, Conrad Becker1, and Klaus Wandelt1 — 1Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, D-53115 Bonn, Germany — 2Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00 664, Warsaw, Poland
Investigations of bimetallic systems with regard to their surface composition and morphology are of great importance for the development of new catalysts. In this work the compositional, electronic and structural properties of thin Au films deposited on a Pd(111) single crystal have been studied by ultraviolet photoelectron spectroscopy (UPS), photoemission of adsorbed xenon (PAX) and CO titration as a function of film thickness (ranging from submonolayer amounts up to multilayers) and temperature. The surface morphology of the system Au on Pd(111) exhibits a strong temperature dependence. Depositing Au at 150 K results in closed films, which undergo a smoothening of the topmost atomic layer by annealing the sample up to 250 K. At a surface temperature of 450 K the Au-Pd intermixing begins at the interface between substrate and overlayer eventually reaching the outermost surface at annealing temperatures of 650 K. Annealing to 850 K and above results in a fast Au depletion in the surface region, which is completed at 1050 K. Additionally performed reaction studies of the partial hydrogenation of butadiene to 1-butene using temperature programmed desorption (TPD) have shown a significant improvement of the catalytic properties of the alloyed Au-Pd surface compared to pure Pd(111).