Adsorption of CO on Rutile TiO2 (110)-1 x 1 Surface with Preadsorbed O Adatoms

We report the investigation on the adsorption behaviors of CO on the rutile TiO2(110)-1 x 1 surface with preadsorbed O adatoms using scanning tunneling microscopy (STM) joint with density functional theory (DFT) calculations. The STM experimental results show that the diffusive CO molecules tend to adsorb at the site close to the O adatoms, forming CO-O and CO-O-CO complexes. These complexes are quite stable against the high bias voltages and UV illumination. DFT calculations give an activation energy barrier of 0.56 eV for CO oxidation through the CO-O complex to produce CO2. Our experimental and theoretical results both indicate that the dissociative O-2, that is, the O adatoms on TO4+, may not be directly responsible for the catalytic oxidation at low temperature.