Performance and redox stability of a double–layer Sr2Fe1.5Mo0.5O6-δ – based electrode for solid state electrochemical application

Abstract

The development of solid oxide electrochemical devices with symmetrical electrodes, is a promising direction in the field of resource saving and green energy. A feature of symmetrical electrodes is their stability to reduction–oxidation (redox) cycling, which can be useful in the case of carbon or sulphur deposition on a fuel electrode. The results of studies of a double-layer symmetrical electrode, where the functional layer consist of 50 wt.% Sr2Fe1.5Mo0.5O6-δ + 50 wt.% Ce0.8Sm0.2O1.9-δ and the collector is Sr2Fe1.5Mo0.5O6-δ are presented for the first time. It was shown that the introduction of Ce0.8Sm0.2O1.9-δ into the electrode functional layer, as well as the use of the current layer, does not lead to a change in the mechanism of oxygen reduction and hydrogen oxidation reactions. An analysis of the fuel cell impedance spectra by the distribution of relaxation times (DRT) method and comparison of the DRT functions with the results of the analysis of symmetric cells made it possible to conclude that during redox cycling the resistance of the oxygen exchange stage increases. It has been suggested that the cause of this is the formation of iron under reducing conditions, followed by its oxidation to oxide in an oxidizing atmosphere.