Staykov, Aleksandar Tsekov

Density functional theory and low energy ion scattering spectroscopy were applied to study the mechanism of oxygen dissociation on the SrO-terminated surfaces of strontium titanate (SrTiO_3) and iron-doped strontium titanate (SrTi1–xFexO_3−δ). Our study reveals that while O_2 dissociation is not favored on the SrO-terminated perovskite surface, oxygen vacancies can act as active sites and catalyze the O–O bond cleavage. Electron transfer from lattice oxygen atoms to the O_2 molecule, mediated by the subsurface transition metal cations, plays an important role xvi in the resulting formation of surface superoxo species. The O_2 molecule dissociates to produce oxygen ions, which are incorporated into the perovskite lattice, and highly active oxygen radicals on the perovskite surface, which further recombine to O_2 molecules. Our focus on the SrO-terminated surface, rather than the TiO_2 layer, which is presumed to be more catalytically active, was driven by experimental observation using low energy ion scattering spectroscopy, which reveals that the surface of SrTiO_3 after high temperature heat treatment is SrO-terminated, and hence this is the surface that is technologically relevant for devices such as solid oxide fuel cells (SOFCs). Our study demonstrates that although the more active BO_2-perovskite layer is not exposed at the gas–solid interface, the SrO-terminated surfaces also actively participate in oxygen exchange reaction [1,2]

Oxygen Activation and Dissociation on Transition Metal Free Perovskite Surfaces

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