First principles study of CO oxidation on TiO2(110): The role of surface oxygen vacancies

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Abstract
The reactivities of the stoichiometric and partially reduced rutile TiO 2 (110) surfaces towards oxygen adsorption and carbon monoxide oxidation have been studied by means of periodic density functional theory calculations within the Car–Parrinello approach. O 2 adsorption as well as CO oxidation are found to take place only in the presence of surface oxygen vacancies (partially reduced surface). The oxidation of CO by molecularly adsorbed O 2 at the O-vacancy site is found to have an activation energy of about 0.4 eV. When the adsorbed O 2 is dissociated, the resulting adatoms can oxidize incoming gas-phase CO molecules with no barrier. In all studied cases, once CO is oxidized to form CO 2 , the resulting surface is defect-free and no catalytic cycle can be established.