Unraveling\nthe Oxygen Vacancy–Performance Relationship\nin Perovskite Oxides at Atomic Precision via Precise Synthesis

Understanding\nthe fundamental effect of the oxygen vacancy atomic\nstructure in perovskite oxides on catalytic properties remains challenging\ndue to diverse facets, surface sites, defects, etc. in traditional\npowder catalysts and the inherent structural complexity. Through quantitative\nsynthesis of tetrahedral (LaCoO<sub>2.5</sub>-T), pyramidal (LaCoO<sub>2.5</sub>-P), and octahedral (LaCoO<sub>3</sub>) epitaxial thin films\nas model catalysts, we demonstrate the reactivity orders of active-site\ngeometrical configurations in oxygen-deficient perovskites during\nthe CO oxidation model reaction: CoO<sub>4</sub> tetrahedron >\nCoO<sub>6</sub> octahedron > CoO<sub>5</sub> pyramid. Ambient-pressure\nCo\nL-edge and O K-edge XAS spectra clarify the dynamic evolutions of\nactive-site electronic structures during realistic catalytic processes\nand highlight the important roles of defect geometrical structures.\nIn addition, in situ XAS and resonant inelastic X-ray scattering spectra\nand density functional theory calculations directly reveal the nature\nof high reactivity for CoO<sub>4</sub> sites and that the derived\nshallow-acceptor defect levels in the band structure facilitate the\nadsorption and activation of reactive gases, resulting in more than\n23-fold enhancement for catalytic reaction rates than CoO<sub>5</sub> sites.