In-Situ and Ex-Situ Fe K-Edge X-Ray Absorption Spectroscopic Studies for the Structural and Electronic Evolution of Strontium Ferrite upon Electrochemical Oxidation

A structural evolution from SrFeO,S(brownmillerite) to SrFeO,(perovskite) upon electrochemical oxidation has been systematically studied by in-situ and ex-situ X-ray Diffraction(XRD) and X-ray absorption spectroscopy(XAS). According to the XRD analysis, the orthorhombic SrFeOIS has been gradually converted to the cubic SrFeO, as the reaction proceeds. The mostly oxidized perovskite could be been obtained after 66 h, From the in-situ and ex-situ Fe K-edge XANES study, it has been found that the degree of oxidation goes to a maximum after 48 h and 30 h for the bulk and the surface, respectively. EXAFS results are also consistent with the above findings from the fact that no peak evolution could be observed after 48 h and 30 h for both ex-situ and in-situ studies, respectively.