Dresden 2009 – scientific programme
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O: Fachverband Oberflächenphysik
O 30: Metal substrates: Adsorption of organic / bio molecules IV
O 30.6: Talk
Wednesday, March 25, 2009, 11:45–12:00, SCH A118
Tuning surface reactivity by alloying - Acrolein adsorption on well ordered PtxCe/Pt(111) alloys — •Jan Markus Essen, Conrad Becker, and Klaus Wandelt — Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstrasse 12, D-53115 Bonn, Germany
The reactivity of Pt(111) surfaces towards acrolein is mainly determined by the d-band molecule interaction at the Fermi edge. Depending on the initial coverage a η4-trans, a η3-cis and a η2-cis and -trans conformation of adsorbed acrolein is stable. A Pt-O interaction is not favored. Acrolein decomposition proceeds via C1-C2 bond cleavage by a Pt addition into the C-C bond which leads mainly to CO and ethene. In contrast to that, the reactivity of acrolein on pure polycrystalline cerium films is mainly caused by the stability of simultaneously generated cerium oxides. A Ce-O interaction is favored which leads to a strongly distorted adsorption geometry. The decomposition proceeds via C1-O bond cleavage by a reductive coupling forming benzene and 1,3,5-hexatriene. Alloying of cerium with Pt results in the formation of several well ordered alloy phases. In general these phases have the same adsorption properties in common. Acrolein adsorbs on the topmost Pt-layer in the same conformation as on Pt(111). Only the η4 conformation is not stable caused by ensemble effects. In contrast to pure Pt(111) however no decomposition takes place. Acrolein desorbs completely intact from these alloy phases at about 230 K.