FeO₆ Octahedral Distortion Activates Lattice Oxygen in Perovskite Ferrite for Methane Partial Oxidation Coupled with CO₂ Splitting

Abstract

Modulating lattice oxygen in metal oxides that conducts partial oxidation of methane in balancing C-H activation and syngas selectivity remains challenging. This paper describes the discovery of distorting FeO₆ octahedra in La_1-<i>x</i>Ce_<i>x</i>FeO₃ (<i>x</i> = 0, 0.25 0.5, 0.75, 1) orthorhombic perovskites for the promotion of lattice oxygen activation. By combined electrical conductivity relaxation measurements and density functional theory calculations studies, this paper describes the enhancement of FeO₆ octahedral distortion in La_1-<i>x</i>Ce_<i>x</i>FeO₃ promoting their bulk oxygen mobility and surface oxygen exchange capability. Consequently, La_0.5Ce_0.5FeO₃ with the highest FeO₆ distortion achieves exceptional syngas productivity of ∼3 and 8 times higher than LaFeO₃ and CeFeO₃, respectively, in CH₄ partial oxidation step with simultaneous high CO₂ conversion (92%) in the CO₂-splitting step at 850 °C. The results exemplify the feasibility to tailor the active lattice oxygen of perovskite by modulating the distortion of BO₆ in ABO₃, which ultimately influences their reaction performance in chemical looping processes.