Electrochemical Oxidation of BaFeO2.5 to BaFeO3

Defect perovskite-type BaFeO2.5 was oxidized to BaFeO3 by an electrochemical method in an alkaline aqueous electrolyte at 25 °C. With increase in the charge transfer q (electrons/formula unit), BaFeOz showed monoclinic (at nearly q = 0), rhombohedral (at around q = 0.34), pseudo-cubic (at 0.78 ≤ q ≤ 0.89), and true cubic (at q ≥ 0.89) structures. While an oxygen evolution reaction (OER) started at ca. q = 0.80, the oxidation of BaFeOz could concurrently be continued with the OER and BaFeO3 was obtained at q = 1.2. Further, the chemical potential of oxygen in BaFeOz could be estimated in the range of 2.5 ≤ z ≤ 2.87 without OER