Exploring Reversible Redox behavior in the 6H-BaFeO3-d (0 < d < 0.4) System. Impact of Fe3+/Fe4+ Ratio on Catalytic Properties.

This work is devoted to evaluating the relationship between oxygen content and catalytic activity on the CO oxidation process of the 6H-type BaFeO3-δ system, showing that a higher Fe oxidation state improved the catalytic performance of the oxides, confirming the involvement of the lattice oxygen in the catalytic process. The redox behavior of the catalyst, followed mainly by neutron thermodiffraction under different atmospheres, allows us to determine the structure of the anionic and cationic sublattices showing a structural transition from the hexagonal symmetry (P63/mmc) of the ideal 6H type to orthorhombic (Cmcm) caused for the octahedra distortion when the Fe3+ concentration increases up to 40% (δ values higher than 0.2) The redox process is topotactic and the 6H basic structure is maintained in the δ range (0<δ<0.4).