ELECTROCHEMICAL OXYGEN INTERCALATION INTO OXIDE NETWORKS

The electrochemical oxidation of Sr2Fe2O5 brownmillerite-type ferrite and La2MO4 (M = Ni, Cu) oxides is reviewed. The oxidation process appears as a very powerful method for preparing high oxidation states of transition-metal oxides. The characterization of the reaction products shows that they are well described as intercalation compounds of oxygenated anions. The fact that the intercalated species are the same as the host anions distinguishes these materials from most other intercalated compounds, in which guest species usually are chemically different from the host ions. The question of the nature and site of the intercalated species as well as that of their diffusion into the sample bulk is discussed on the basis of various characterizations and physical measurements as well as within the scope of recent considerations of the electronic distribution in oxides of transition elements in a high oxidation state. © 1992 Academic Press, Inc.