Interaction of CO with planar Au/TiO2 model catalysts at elevated pressures

The interaction of CO with structurally well-defined, planar Au/TiO2 model catalysts at elevated pressures (up to 50 mbar) was studied in-situ by polarization-modulated infrared reflection absorption spectroscopy and ex-situ by X-ray photoelectron spectroscopy performed before and after CO exposure. The results indicate a CO-induced partial reduction of the oxide surface, which is evidenced by a low frequency C-O vibration at 2060 cm(-1), combined with a spreading of the An nanoparticles due to a modification of the Au-oxide interface energy. In a 2:1 CO:O-2 atmosphere, TiO2 support reduction was not observed, and a pre-reduced surface was re-oxidized. The consequences of these results for the understanding of the CO oxidation mechanism on Au/TiO2 (model) catalysts are discussed.