title: Supports and modified nano-particles for designing model catalysts.
abstract: In order to design catalytic materials, we need to understand the essential causes for material properties resulting from its composite nature. In this paper we discuss two, at first sight, diverse aspects: (a) the effect of the oxide-metal interface on metal nanoparticle properties and (b) the consequences of metal particle modification after activation on the selectivity of hydrogenation reactions. However, these two aspects are intimately linked. The metal nanoparticle's electronic structure changes at the interface as a catalyst is brought to different reaction temperatures due to morphological modifications in the metal and, as we will discuss, these changes in the chemistry lead to changes in the reaction path. As the morphology of the particle varies, facets of different orientations and sizes are exposed, which may lead to a change in the surface chemistry as well. We use two specific reactions to address these issues in some detail. To the best of our knowledge, the present paper reports the first observations of this kind for well-defined model systems. The changes in the electronic structure of Au nanoparticles due to their size and interaction with a supporting oxide are revealed as a function of temperature using CO2 activation as a probe. The presence of spectator species (oxopropyl), formed during an activation step of acrolein hydrogenation, strongly controls the selectivity of the reaction towards hydrogenation of the unsaturated C[double bond, length as m-dash]O bond vs. the C[double bond, length as m-dash]C bond on Pd(111) when compared with oxide-supported Pd nanoparticles.
authors.affiliation: US Army Research Laboratory, USA.
authors.forename: C P
authors.initials: CP
authors.lastname: O'Brien
authors.affiliation: Fritz Haber Institute of the Max Planck Society, Department of Chemical Physics, Faradayweg 4-6, 14195 Berlin, Germany. freund@fhi-berlin.mpg.de.
authors.forename: K-H
authors.initials: KH
authors.lastname: Dostert
authors.affiliation: Institute of Physics, University of Graz, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Hollerer
authors.affiliation: Fritz Haber Institute of the Max Planck Society, Department of Chemical Physics, Faradayweg 4-6, 14195 Berlin, Germany. freund@fhi-berlin.mpg.de.
authors.forename: C
authors.initials: C
authors.lastname: Stiehler
authors.affiliation: Fritz Haber Institute of the Max Planck Society, Department of Chemical Physics, Faradayweg 4-6, 14195 Berlin, Germany. freund@fhi-berlin.mpg.de.
authors.forename: F
authors.initials: F
authors.lastname: Calaza
authors.affiliation: Fritz Haber Institute of the Max Planck Society, Department of Chemical Physics, Faradayweg 4-6, 14195 Berlin, Germany. freund@fhi-berlin.mpg.de and Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Schauermann
authors.affiliation: Fritz Haber Institute of the Max Planck Society, Department of Chemical Physics, Faradayweg 4-6, 14195 Berlin, Germany. freund@fhi-berlin.mpg.de.
authors.forename: S
authors.initials: S
authors.lastname: Shaikhutdinov
authors.affiliation: Institute of Physics, University of Graz, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Sterrer
authors.affiliation: Fritz Haber Institute of the Max Planck Society, Department of Chemical Physics, Faradayweg 4-6, 14195 Berlin, Germany. freund@fhi-berlin.mpg.de.
authors.forename: H-J
authors.initials: HJ
authors.lastname: Freund