Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 73: Symposium: Bimetallic Nanosystems: Tuning Physical and Chemical Properties II (Invited Speakers: André Fielicke, Thomas Risse, Jürgen Behm)

O 73.9: Vortrag

Donnerstag, 28. Februar 2008, 17:00–17:15, MA 005

Decomposition of methanol by Pd, Co and bimetallic Co-Pd catalysts: model studies bridging the pressure gap — Tobias Nowitzki¹, Holger Borchert¹, Birte Jürgens¹, Peter Behrend², Yulia Borchert¹, Thomas Risse³, •Volkmar Zielasek¹, Suzanne Giorgio⁴, Claude R. Henry⁴, and Marcus Bäumer¹ — ¹Institut für Angewandte und Physikalische Chemie, Universität Bremen — ²UFT, Universität Bremen — ³Fritz-Haber-Institut der Max-Plack-Gesellschaft, Berlin — ⁴CRMCN-CNRS, Campus de Luminy, Marseille

Bimetallic particles may exhibit catalytic activities which reach far beyond those of the monometallic components. For the Co/Pd combination which is, e.g., of technological relevance for the hydrogenation of CO on the route from natural gas to liquid fuel, we have studied the interaction of model catalysts with methanol in order to obtain mechanistic information on decomposition reactions. In UHV studies, STM, TPD and XPS were performed at mono- and bimetallic nanoparticles prepared by PVD on thin epitaxial alumina films on NiAl(110). In comparison, the performance of Co/Pd nanoparticles, wet-chemically prepared on MgO, was studied in continuous flow reactors using DRIFTS and gas phase analysis at ambient pressure. This dual approach provides a consistent picture: The decomposition of methanol proceeds in two reaction pathways, the relative importance of which varies with the particle compositions. CO desorption is the limiting factor for activity at lower temperatures. Although electronic effects in the bimetallic system facilitate CO desorption, they do not compensate the lower intrinsic activity of Co sites compared to Pd sites.