The reduction of a thin surface oxide on the Rh(111) surface by CO is studied in-situ by photoemission spectroscopy, scanning tunneling microscopy, and density functional theory. CO molecules are found not to adsorb on the surface oxide at a sample temperature of 100 K, in contrast to on the clean and chemisorbed oxygen covered surface. Despite this behavior, the surface oxide may still be reduced by CO, albeit in a significantly different fashion as compared to the reduction of a phase containing only chemisorbed on-surface oxygen. The experimental observations combined with theoretical considerations concerning the stability of the surface oxide result in a model of the reduction process at these pressures suggesting that the surface oxide behaves as a source of oxygen for the CO-oxidation reaction.
Corresponding author: E. Lundgren. Reprints also available from M. Schmid (schmid).
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