Adsorption and reaction of CO and CO2 on oxidized and reduced SrTiO3(100) surfaces

The adsorption and reaction of CO and CO2 on oxidized and reduced SrTiO3(100) surfaces have been studied with temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). XPS results indicate that the oxidized SrTiO3(100) surfaces are nearly defect-free with predominantly Ti4+ ions whereas the sputter-reduced surfaces contain substantial amounts of defects. Both CO and CO2 are found to adsorb weakly on the oxidized SrTiO3(100) surfaces. On sputter-reduced surfaces, enhanced reactivity of CO and CO2 is observed due to the presence of oxygen vacancy sites, which are responsible for dissociative adsorption of these molecules. Our studies indicate that the CO and CO2 molecules exhibit relatively weaker interactions with SrTiO3(100) compared to those with TiO2(100) and TiO2(100) surfaces. This is most likely an influence of the Sr cations on the electronic structure of the Ti cations in the mixed oxide of SrTiO3.