Oxidation reactions over RuO2: A comparative study of the reactivity of the (110) single crystal and polycrystalline surfaces

The present work is devoted to the investigation of oxidation reactions ove r RuO2 surfaces. Two main points are addressed. First, on the fundamental l evel, a detailed investigation of the site requirement for CO (as well as f or methanol) and O-2 adsorption on the surface of a well-defined RuO2(110) crystal is conducted. Second, a comparison with polycrystalline RuO2 toward these oxidation reactions is presented. Both results, those in UHV over Ru O2 (110) and those at atmospheric pressure over polycrystalline RuO2, agree fairly well. This indicates that the surface chemistry of the (110) single crystal is very similar to that of the polycrystalline material. Both the activity of the RuO2(110) surface in the UHV regime and the activity of pol ycrystalline RuO2 in the high-pressure regime were investigated by temperat ure-programmed desorption and by X-ray photoelectron spectroscopy. The reas ons for the unusually high catalytic activity for oxidation reactions of Ru O2 are traced back to the strong bonding of the reactants over the undercoo rdinated Ru atoms together with the presence of weakly bound undercoordinat ed oxygen species, serving as the oxidizing agent. (C) 2001 Academic Press.