DFT modelling of the CO-NO redox reaction at Cu-doped SrTiO3(1 0 0) stepped surface: CO oxidation at lattice O ions

CO and NO represent a large fraction of the toxic emission from automobile exhausts. Catalytic converters exploit processes where these compounds are transformed in harmless species (CO2 and N2). Our aim is to use the DFT to study the suitability of a cheap perovskite (SrTiO3) to catalyze the redox reaction between CO and NO. In particular, we want to understand the interplay between the effects of Cu doping/steps. Moreover, the thermodynamics of CO oxidation at flat and stepped SrTiO3(1 0 0) surfaces is compared, both for the pure host and for the Cu-doped material. Here, we focus on the first part of the reaction, where CO is oxidized by the lattice O atoms. We compare results from pure and Cu-doped slabs by considering several reaction pathways based on the Mars-van Krevelen mechanism. We find that Cu doping and steps strongly affect the reaction mechanism, but in all the proposed pathways there is at least an endothermic step. In general, steps do not provide active sites for the redox reaction between CO and NO. For the Cu doped step this is due to the strong stability of oxygen vacancies at the facet sites that prevents further reactions.