Abstract
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 SrTiO3(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.
Highlights
Perovskite oxide surfaces catalyze oxygen exchange reactions that are crucial for fuel cells, electrolyzers, and thermochemical fuel synthesis
Our results reveal the polyhedral flexibility up to the ideal coordination limit as an important and previously unexplored factor that can govern the reactivity to oxygen exchange reactions on perovskite oxides surfaces
Our experimental and computational results are at odds with the commonly accepted models for oxygen exchange mentioned above, effects i.e., that afvaaciillaitbaitleityeleacntdromn otrbainlitsyfeor1f1V–1O4s. 6O–1u0r and the electronic experimental and theoretical methods allow us to independently assess these factors: their values suggest a higher reactivity of the (2 × 5) structure, the opposite of what is observed in the 18O experiments
Summary
Perovskite oxide surfaces catalyze oxygen exchange reactions that are crucial for fuel cells, electrolyzers, and thermochemical fuel synthesis. 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. We take SrTiO3 as a prototypical model perovskite oxide, primarily due to our ability to prepare SrTiO3(110) with two distinctly different and controllable surface phases with solved structures[31]. Another advantage of this system is the fact that Sr segregation is suppressed if single-crystal SrTiO3 surfaces are stabilized by a reconstruction[32]. Our results reveal the polyhedral flexibility up to the ideal coordination limit as an important and previously unexplored factor that can govern the reactivity to oxygen exchange reactions on perovskite oxides surfaces
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