Visualization of atomic processes on ruthenium dioxide using scanning tunneling microscopy

H. Over1, M. Knapp1, E. Lundgren2, A.P. Seitsonen3, M. Schmid4, P. Varga4

1Dept. of Physical Chemistry, Justus-Liebig-Universität Gießen, 35392 Gießen, Germany
2Department of Synchrotron Radiation Research, Institute of Physics, Lund University, 22100, Lund, Sweden
3Physikalisch Chemisches Institut, Universität Zürich, 8057 Zürich, Switzerland
4Institut für Allgemeine Physik, Technische Universität Wien, 1040 Wien, Austria

Chem. Phys. Chem. 5 (2004) 167-174

The visualization of surface reactions on the atomic scale provides direct insight into the microscopic reaction steps taking place in a catalytic reaction at a (model) catalyst's surface. Employing the technique of scanning tunneling microscopy (STM), we have investigated the CO oxidation reaction over the RuO2(110) and RuO2(100) surfaces. For both surfaces the protruding bridging O atoms are imaged in STM as bright features. The reaction mechanism is identical on both orientations of RuO2. CO molecules adsorb on the undercoordinated surface Ru atoms from where they recombine with undercoordinated O atoms to form CO2 at the oxide surface. In contrast to the RuO2(110) surface, the RuO2(100) surface stabilizes also a catalytically inactive c(2x2) surface phase onto which CO is not able to adsorb above 100 K. We argue that this inactive RuO2(100)-c(2x2) phase may play an important role in the deactivation of RuO2 catalysts in the electrochemical Cl2 evolution and other heterogeneous reactions.

Corresponding author: H. Over (University Giessen). Reprints also available from M. Schmid (schmid< encoded email address >).

Users with online access to ChemPhysChem can load the article from the publisher.