Parts | Days | Selection | Search | Downloads | Help
O: Oberflächenphysik
O 15: Hauptvortrag
O 15.1: Invited Talk
Tuesday, March 27, 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.