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 55.19: Poster
Mittwoch, 27. Februar 2008, 18:30–19:30, Poster F
Mass selected Ag cluster based catalysis: size and shape effects — •Kristian Sell1, Ingo Barke1, Viola von Oeynhausen1, Karl-Heinz Meiwes-Broer1, Stefan Vajda2, Sungsik Lee2, Yu Lei2,3, Byongdu Lee2, Jeffrey W. Elam2, Michael J. Pellin2, Sönke Seifert2, Randall E. Winans2, Randall J. Meyer2, and Arantxa Fraile-Rodríguez4 — 1Universität Rostock, Institut für Physik, Rostock, Deutschland — 2Argonne National Laboratory, Argonne, USA — 3University of Illinois at Chicago, USA — 4Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland
The exceptional performance of nanocatalysts has motivated intense research as highly dispersed nanocatalysts are widely used in commercial applications. Here we study size-selected silver particles under realistic conditions in a reaction of industrial relevance.
Supported size selected Ag clusters of sub-nm to several nm size are produced by laser evaporation and an arc charge ion source (ACIS) and deposited on Al2O3 supports. These are prepared by atomic layer deposition of thin Al2O3 films on the native silicon oxide surface of Si wafers. The catalytic properties of the supported clusters are studied under atmospheric pressure reaction conditions. We use a unique approach which allows for in situ, real-time monitoring of changes in size and shape of the nanocatalysts by grazing-incidence small-angle x-ray scattering (GISAXS) with simultaneous detection of the reaction products. The relationship between cluster size/shape and its function in catalytic activity and selectivity in direct epoxidation of propylene on Ag clusters will be discussed.