Investigation of the active site and the mode of Au/TiO2 catalyst deactivation using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS)

CO is a useful probe in the characterization of surface properties of both metal and metal oxide via adsorption. Adsorption of CO was used to monitor the possible active site of an Au/TiO₂ catalyst for the CO oxidation reaction. CO adsorption on the reduced catalyst results in the band at 2104 cm⁻¹ indicative of Au⁰. During the reaction (in the presence of both CO and O2 present) the band is shifted to higher wave numbers indicating non-competitive adsorption on the surface of Au species. This study also reveals the relationship between the presence of CO (in the absence of oxygen) and the build-up of surface species such as bicarbonates, formates and carbonate species which decreases the activity of the catalyst. The presence of both the reduced and the cationic species of Au seem to be requirement for the activity of the catalyst.