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O: Fachverband Oberflächenphysik

O 50: Particles and Clusters II

O 50.4: Vortrag

Donnerstag, 29. März 2007, 12:00–12:15, H38

Oxidation / reduction cycles of metal nanoparticles — •A. Stierle, N. Kasper, P. Nolte, N. Y. Jin-Phillipp, and H. Dosch — Max Planck Institut für Metallforschung, Heisenbergstr. 3, D-70569 Stuttgart, Germany

During catalytic reactions, oxide supported transition metal nanoparticles undergo continuously oxidation / reduction cycles. We have performed in-situ x-ray diffraction studies at the MPI-MF beamline at the Ångström Quelle Karsruhe (ANKA) and at beamline BM32 at the European Synchrotron Radiation Facility (ESRF) during the oxidation and reduction of different epitaxial nanoparticle / oxide support systems (Rh, Pd/MgO(100), Rh,Pd/Al₂O₃(0001), Pd/ZnO(0001), particle size 5-10 nm), thereby closing the pressure gap from near-UHV to atmospheric pressures. The oxidation properties of nanoparticles is expected to depend on the support, their orientation and their size and shape. We observe that the particles undergo at 500 K reversible shape changes when changing from reducing to oxidizing conditions and back. Under oxidizing conditions the formation of new facets is observed and in the case of Rh/MgO(100) the evolution of a surface reconstruction. The shape of the nanoparticles is additionally characterized by ex-situ high resolution transmission electron microscopy.

Financial support is acknowledged from the European Union under contract no. NMP3-CT-2003-505670 (NANO₂).