Catalytic Mechanisms of NO Reduction in a CO-NO Atmosphere at Co- and Cu-Doped SrTiO3(100) Surfaces

The NO reduction in a CO-NO atmosphere at the Co- and Cu-doped SrTiO3(100) surfaces is investigated by density functional theory calculations. The energy profiles for several mechanisms are computed and compared. On this basis, a rationale for the available experimental data is proposed. Oxygen vacancies formed as intermediate species in the CO oxidation process play a key role in the NO reduction. Their concentration is also relevant because, if low, formation of N2O prevails on that of N2, leading to an incomplete reduction. The formation of oxygen vacancies is favored by Co and Cu impurities, the latter being most effective. Overall, doping promotes the catalytic reduction of NO on SrTiO3.