Berlin 2005 – wissenschaftliches Programm
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O: Oberflächenphysik
O 3: Oberfl
ächenreaktionen I
O 3.7: Vortrag
Freitag, 4. März 2005, 12:15–12:30, TU EB420
Surface Diffusion and Fluctuations on Catalyst Nanoparticles — •Mathias Laurin1, Viktor Johánek1, Ann W. Grant2, Bengt Kasemo2, Jörg Libuda1, and Hans-Joachim Freund1 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4–6, 14195 Berlin, Germany — 2Department of Applied Physics, Chalmers University of Technology, 41296, Göteborg, Sweden
The CO oxidation and oxygen diffusion kinetics are investigated using molecular beam methods under ultrahigh vacuum (UHV). We employ oxide supported Pd nanoparticles prepared by physical vapor deposition (PVD) and electron beam lithography (EBL) covering a large range of particle sizes (1–500 nm).
The angular resolved distribution of CO2 depends on the reaction conditions and particle size. In combination with the experiments, microkinetic simulations give information on the mobility of the adsorbed species under reaction conditions and on the local reaction rates on the particle surface.
A macroscopic bistability of the reaction is observed at low temperatures on the big particles. It is however quenched on small nanoparticles. This is attributed to fluctuation induced transitions, accelerated in the presence of defect sites.