Regensburg 2007 – scientific programme
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O: Fachverband Oberflächenphysik
O 68: Metal Substrates: Adsorption V
O 68.5: Talk
Friday, March 30, 2007, 11:15–11:30, H39
Adsorption of Deuterium and CO on PdRu surface alloys studied by temperature programmed desorption — •Heinrich Hartmann, Thomas Diemant, Joachim Bansmann, and Juergen Behm — Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm
The adsorption properties of Pd/Ru surface alloys on Ru(0001) were investigated by Temperature Programmed Desorption using D2 and CO as probe molecules. The surface alloys were created by depositing Pd on a Ru(0001) crystal and subsequent annealing to 1100 K. This results in the replacement of Ru by Pd atoms in the first surface layer. Earlier STM experiments showed a tendency for phase separation between Pd and Ru in the alloy surface. The TPD experiments showed a lower adsorption energy for CO and D2 on the bimetallic alloy surfaces with respect to Ru(0001) and Pd(111) surfaces, this has been attributed to electronic and ensemble effects on the Pd/Ru surface. Concomitantly the saturation coverage and initial sticking coefficients of D2 were found to decrease for higher Pd-contents, indicating an activation barrier for D2 adsorption on the bimetallic surfaces, whereas the saturation coverage and initial sticking coefficients of CO remained unchanged with respect to adsorption on Ru(0001). Concurrently, a shift of the high-temperature end of the spectra to lower temperatures was observed for both adsobates, indicating a destabilization of the remaining Ru adsorption sites or a faster desorption process due to diffusion between adsorption sites of different bonding strength.