From these results, the question arises whether a more oxidized phase, incorporating a larger amount of (Fe 4+ ), will exhibit higher activity. Regarding the availability of the corresponding materials, a few examples in the literature have reported the obtention of fully oxidized BaFeO3 but not with the 6H type structure, which precludes a proper comparison with previous catalytic results. In this regard, a fully oxygenated (hhc)3-12R BaFeO3 has been obtained by high-pressure synthesis, starting from an oxygen-deficient 6H-BaFeO3-δ as a precursor, but this method is not suitable for heterogeneous catalysis, as the obtained solids present large particle size. Topotactic oxidation with ozone appears as a less aggressive procedure. Thus, in an original publication by Kageyama's group, BaFeO2.5 was first obtained by spray pyrolysis. Then, further treatment under ozone led to a cubic 3C-BaFeO3 polytype.