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MO: Molekülphysik

MO 2: Clusters I: Metal Clusters (joint session A and MO)

MO 2.5: Vortrag

Montag, 2. April 2001, 16:45–17:00, H1012

Temperature dependent reactions of small gold clusters with oxygen and carbon monoxide — •Liana D. Socaciu¹, Jan Hagen¹, Ueli Heiz², Thorsten M. Bernhardt¹, and Ludger Wöste¹ — ¹Freie Universität Berlin, Institut für Experimentalphysik, Arnimallee 14, D-14195 Berlin, Germany — ²Ecole Polytechnique Federale de Lausanne, Institut de Physique Experimentale, CH-1015 Lausanne, Switzerland

While bulk gold material is chemically inert towards O₂ and CO, gold nanoparticles exhibit remarkable catalytic properties in the CO oxidation [1]. Recently, it was shown that the charge transfer between the oxide support and the adsorbate is essential for the catalytic activity of gold clusters [2]. From this point of view it is important to make a comparative study of the chemical properties of supported and gas phase clusters. We investigate the reactivity of charged, small, mass-selected Au clusters with O₂ and CO in a temperature variable octopole ion trap. Interestingly, Au₂⁻ adsorbs only one molecule O₂ whereas Au₁⁻ and Au₃⁻ show no evidence for oxidation. In contrast to the O₂ reactions, Au₂⁻ and Au₃⁻ are able to bind two CO molecules. The measured reaction rates at different temperatures are explained with the electronic stability of the cluster complexes as well as with the metal cluster degrees of freedom involved in the cooling process at lower temperature. [1] M. Haruta, Catalysis Today, 36, 153-166, 1997. [2] A. Sanchez, S. Abbet, U. Heiz, W.-D. Schneider, H. Häkkinen, R. N. Barnett, and Uzi Landman, J. Phys. Chem. A, 103, 9573-9578, 1999.

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