It is widely known that surface atomic configuration can affect the reactivity of the oxygen reduction and evolution reaction. But it remains unclear how the oxygen exchange mechanism is influenced by the surface atomic structure, owing to a lack of methods for accurately controlling and probing surface atomic structures under reaction conditions. Now Diebold from TU Wien, Yildiz from MIT and co-workers overcome the challenge and demonstrate that the surface atomic structure is the dominant factor that determines oxygen incorporation on perovskite surfaces.
They prepare 0.5 wt% Nb-doped SrTiO3(110) with (4 × 1) and (2 × 5) surface phase symmetries. These two surface structures are demonstrated to be stable with no observable Sr segregation when treated in oxygen atmosphere. The researchers then monitor the 18O-labelled oxygen exchange kinetics on these two reconstructions at 450 °C. The reactivity on the (4 × 1) surface phase is found to be three times that on the (2 × 5) phase. This acceleration cannot be interpreted through the conventional vacancy, work function or band-bending models in density functional theory calculations. Instead, it is the atomic structure that determines the oxygen adsorption and dissociation. The higher the polyhedral flexibility, the faster is the oxygen incorporation.
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Sun, W. Beyond traditional reactivity models. Nature Nanotech 13, 874 (2018). https://doi.org/10.1038/s41565-018-0286-9