Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 73: Symposium: Bimetallic Nanosystems: Tuning Physical and Chemical Properties II (Invited Speakers: André Fielicke, Thomas Risse, Jürgen Behm)
O 73.6: Vortrag
Donnerstag, 28. Februar 2008, 16:15–16:30, MA 005
Ligand versus ensemble effects in the adsorption on nanostructured bimetallic surfaces — Sung Sakong1, Yoshihiro Gohda2, and •Axel Groß3 — 1Fachbereich Physik, Universität Duisburg-Essen, Duisburg, Germany — 2Department of Applied Physics, The University of Tokyo, Japan — 3Institut für Theoretische Chemie, Universität Ulm, Germany
We have performed total energy calculations based on density functional theory addressing the reactivity of nanostructured bimetallic surface alloys. The catalytic activity of alloys is determined by electronic, geometric and structural factors which are often summarized employing the terms ligand and ensemble effects. Using the systems PdCu [1] and PtAu [2] as examples, we show that bimetallic systems can exhibit properties that do not correspond to an intermediate behavior in between those of the pure components but that are rather beyond those of both components [3]. Furthermore, whereas single atoms of the surface alloys can show a decreasing interaction strength with adsorbates (ligand effect), the binding at the most favorable adsorption sites can still become stronger when the concentration of the more reactive metal is increased (ensemble effect). The electronic and geometric effects underlying these phenomena will be addressed.
[1] S. Sakong, C. Mosch, and A. Groß, PCCP 9, 2216 (2007).
[2] Y. Gohda and A. Groß, Surf. Sci. 601, 3702 (2007).
[3] A. Groß, Topics Catal. 37, 29 (2006).