Adsorption of CO and formation of carbonates at steps of pure and Co-doped SrTiO3 surfaces by DFT calculations

A reconstructed SrTiO3 (1 1 0) surface, whose facets are oriented along the {1 0 0} planes, is used to study the reactivity of steps at the (1 0 0) surface. With this aim, we studied the interaction of CO on pure and Co-doped SrTiO3 (1 1 0) facetted surfaces using density functional theory calculations. Results show that steps have peculiar properties: at variance to their terrace counterparts, step-edge O ions can absorb CO molecules. Furthermore, the interaction of CO with co-adsorbed O2 easily gives rise to stable monodentate and bidentate carbonate species, which hamper the formation/desorption of CO2. In this context, Co impurities play a double role: on one hand, they stabilize oxygen vacancies, on the other, they (partially) contrast the formation of carbonate species.