Study demonstrates how perovskite symmetry influences CO oxidation in catalysts, suggesting design strategies.
Platinum group metal-free catalysts can be designed by maximizing the reactivity of structural oxygen in metal oxide catalysts. This study indicates that the symmetry of the perovskite oxide affects the CO oxidation activity and the release behavior of oxygen in the perovskite lattice. Specifically, cubic-type SrTi0.8Co0.2O3 and hexagonal-type BaTi0.8Co0.2O3 showed much higher CO oxidation activities than orthorhombic-type CaTi0.8Co0.2O3. The oxygen-release properties evaluated under H2 flow show that SrTi0.8Co0.2O3 and BaTi0.8Co0.2O3 exhibit better performance and structural stability than CaTi0.8Co0.2O3. Density functional theory calculations of the energy required for the oxygen desorption reveal that the ΔR value, which denotes the difference in the Co–O bond lengths between the oxidized and reduced states of Co-doped ATiO3, is a valid indicator of the oxygen reactivity and structural stability. The ΔR value primarily depends on the symmetry of the crystal structure and the magnetic moment of the Co ion. The structural oxygen in SrTi0.8Co0.2O3 or BaTi0.8Co0.2O3, which have smaller ΔR values than that of CaTi0.8Co0.2O3, can be desorbed at lower energy. This study clearly demonstrates that the reactivity of structural oxygens in a metal oxide catalyst can be controlled by adjusting the symmetry of the perovskite unit.
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Sugimoto et al. (2025) studied this question.
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