PNNL

Abstract

Photo-induced reactions between O2 and CO on reduced rutile TiO2(110) are studied at low temperature (~30K). Photon stimulated desorption (PSD) of O2, CO2 and CO are observed with comparable yields. Isotope labeling experiments indicate that O2 chemisorbed in a vacancy is more active for photooxidation than O2 chemisorbed on a Ti5c site. The angular distribution for the desorbing CO2 is peaked at ~40º with respect to the surface normal in the azimuth (i.e. perpendicular to the bridging oxygen rows) suggesting that CO2 is produced from O2 occupying an oxygen vacancy and CO adsorbed on a Ti5c site next to it. The experimental results are consistent with CO2 being produced from a transition state complex that has been predicted theoretically. The CO PSD from TiO2(110) is enhanced dramatically by the presence of chemisorbed O2 suggesting that it is a by-product of the CO photooxidation process.