Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 64: Metal substrates: Adsorption of inorganic molecules
O 64.4: Vortrag
Freitag, 27. März 2009, 12:00–12:15, SCH A215
CO adsorption on bimetallic PtRu/Ru(0001) surfaces - the influence of surface structure — •Heinrich Hartmann, Thomas Diemant, Joachim Bansmann, and R. Juergen Behm — Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm, Germany
To study the influence of the surface structure on the adsorption properties of PtRu/Ru(0001) surfaces, two types of bimetallic model systems with significantly different surface structure were prepared and studied by a combination of TPD and IR spectroscopy using CO and deuterium as probe molecules. While the first type of surface, a sub-monolayer Pt film on Ru(0001), shows Pt islands on the Ru substrate, the second type is a PtRu surface alloy with an almost random distribution of the components in the surface layer. For both surface types, a marked weakening of the adsorption strength of both CO and deuterium is evidenced by TPD experiments. While the CO TPD measurements show only minor differences for the two surface types, the surface structure has a clear influence on the D2 TPD spectra, which is most pronounced for intermediate Pt concentrations. These results demonstrate the special importance of ensemble effects for deuterium adsorption, where mixed threefold adsorption ensembles are occupied, while such effects are absent for CO with exclusive adsorption in on-top sites. For CO, the influence of ligand and strain effects for the CO adsorption on the bimetallic surfaces will be discussed.