Hamburg 2001 – wissenschaftliches Programm

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O: Oberflächenphysik

O 15: Hauptvortrag

O 15.1: Hauptvortrag

Dienstag, 27. März 2001, 10:15–11:00, B

Ruthenium Dioxide a Fascinating Material to Perform Atomic-Scale Surface Chemistry — •Herbert Over — Fritz-Haber Institut der MPG, Abt. Phys. Chemie, Faradayweg 4-6, D-14195 Berlin

Over the past few years, RuO₂ has developed into one of the best characterized late transition metal oxide in surface science, revealing unique redox properties. In a recent study [1] the CO oxidation reaction over RuO₂(110) was investigated by LEED, STM and DFT calculations, connecting structural with chemical properties. It was demonstrated on atomic scale that the presence of coordinatively unsaturated Ru sites (cus-Ru) is the primary reason for the high activity of RuO₂(110) towards CO oxidation. CO molecules adsorb strongly (adsorption energy of 1.2eV) on-top of these cus-Ru atoms from where the actual oxidation reaction takes place via recombination of the CO molecule with undercoordinated lattice oxygen to form CO₂ (so called Mars-van Krevelen mechanism); the conversion probability of this process is as high as 80 percent. This mechanism involves a reduction of the RuO₂(110) surface. Therefore, equally important for being an efficient catalyst is the propensity of reduced RuO₂ to get re-oxidized by oxygen adsorption. A weakly held oxygen species was found to adsorb on-top of the cus-Ru atoms and which actuates the restoration of the reduced RuO₂ surface. Other simple reactions over RuO₂ will be discussed.

[1] H. Over, Y.D. Kim, A.P. Seitsonen, S. Wendt, E. Lundgren, M. Schmid, P. Varga, A. Morgante, G. Ertl; Science 287 (2000) 1474.