Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 28: Heterogeneous catalysis II

O 28.4: Talk

Tuesday, March 27, 2012, 11:15–11:30, MA 042

Structure and reactivity of PdAg/Pd(111) surface alloys — •Luis Mancera and Axel Groß — Institute of Theoretical Chemistry, Ulm University, D-89069 Ulm, Germany

Bimetallic surface structures often exhibit catalytic activities and selectivities higher than their pure components. Therefore there is a strong interest in understanding the factors leading to the properties of bimetallic catalysts. Surface alloys often serve as model systems for bimetallic catalysts. Very recently, a study of the structural and catalytic properties of PdAg/Pd(111) upon CO exposure was carried out using a combination of various UHV techniques, i.e. STM, TPD and HREELS [1]. This study showed that the activity of this system is mainly driven by ensemble effects, i.e. by the configuration of Pd adsorption sites. It was also found that the CO bonding strength is significantly reduced upon increasing the Ag concentration. In this contribution, we address the reactivity of bimetallic PdAg/Pd(111) surface alloys based on density functional theory (DFT) calculations. Since changes in the relative metal composition often lead to a non-linear variation of their catalytic properties, mainly due to the interplay of electronic ligand and geometrical effects, we investigate their dependence on the concentration and configuration of Ag atoms in the surface alloy. Furthermore, we also study trends in the CO adsorption energies as a function of CO coverage.

[1] Y. Ma, T. Diemant, J. Bansmann and R. J. Behm. Phys. Chem. Chem. Phys. 13, 10741 (2011)