Influence of surface atomic structure demonstrated on oxygen incorporation mechanism at a model perovskite oxide

• Published in: Nature communications Vol. 9; no. 1; pp. 3710 - 9
• Main Authors: Riva, Michele, Kubicek, Markus, Hao, Xianfeng, Franceschi, Giada, Gerhold, Stefan, Schmid, Michael, Hutter, Herbert, Fleig, Juergen, Franchini, Cesare, Yildiz, Bilge, Diebold, Ulrike
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 13-09-2018; Nature Publishing Group; Nature Portfolio
• Subjects: 119/118; 140/146; 147/138; 639/301/119/544; 639/301/299/161/893; Atomic structure; Chemical reactions; Chemical synthesis; Electrolytic cells; Electron transfer; Exchanging; Fuel cells; Fuel technology; Humanities and Social Sciences; Kinetics; Laboratories; Materials science; multidisciplinary; Nuclear fuels; Oxygen; Oxygen exchange; Perovskites; Polyhedra; Reaction kinetics; Science; Science (multidisciplinary); Strontium titanates; Surface analysis (chemical)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-05685-5

Perovskite oxide surfaces catalyze oxygen exchange reactions that are crucial for fuel cells, electrolyzers, and thermochemical fuel synthesis. Here, by bridging the gap between surface analysis with atomic resolution and oxygen exchange kinetics measurements, we demonstrate how the exact surface atomic structure can determine the reactivity for oxygen exchange reactions on a model perovskite oxide. Two precisely controlled surface reconstructions with (4 × 1) and (2 × 5) symmetry on 0.5 wt.% Nb-doped SrTiO
3
(110) were subjected to isotopically labeled oxygen exchange at 450 °C. The oxygen incorporation rate is three times higher on the (4 × 1) surface phase compared to the (2 × 5). Common models of surface reactivity based on the availability of oxygen vacancies or on the ease of electron transfer cannot account for this difference. We propose a structure-driven oxygen exchange mechanism, relying on the flexibility of the surface coordination polyhedra that transform upon dissociation of oxygen molecules.
The availability of surface oxygen vacancies or electrons is often viewed as the defining factor for the reactivity of perovskite oxides. Two precisely controlled surfaces on SrTiO
3
(110) show strikingly different O exchange kinetics, which the authors ascribe to the flexibility of the surface polyhedra.