Adsorption and reactivity of CO at a stepped SrTiO3(100) surface in the presence of Cu impurities

We have performed density functional calculations on a facetted SrTiO3 (1 1 0) surface, a model for stepped (1 0 0) surfaces considering both a pure and a Cu-doped system. The formation of oxygen vacancies and the adsorption of small have been studied in detail. Results show that Cu dopants strongly influence the reactivity of the step, both at the edge and at the facet sites, favoring the formation of oxygen vacancies. The adsorption of small molecules has been studied to obtain information about the role played by the system in catalytic pro- cesses. It is found that adsorption energies of NO, CO, CO2 and O-2 at the vacancies of present in doped steps is always unfavored. The extraction of oxygen atom by direct CO adsorption on the oxidation mechanism has also been investigated for both pure unreduced and for reduced doped steps. In both cases, the desorption of CO2 is an endothermic process, but the presence of the dopant significantly reduces the desorption energies.