Electrochemical Characterisation of a La0.6Sr0.4Co0.2Fe0.8O3−δ Cathode for IT-SOFCs

The electrochemical properties of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) cathodes were assessed to determine whether LSCF cathodes could be adequate for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Two-electrode impedance and three-electrode measurements were carried out to investigate the kinetics of the oxygen reduction reaction under various temperatures, oxygen partial pressures and polarisations. A change in rate-determining step at about 600°C was suggested by the results. It is proposed that LSCF perovskite behaves as a mixed ionic electronic conductor (MIEC) in the highest temperature range, the oxygen reduction occurring throughout the electrode thickness and being stimulated by the formation of oxygen vacancies. However below 600°C bulk diffusion seems to limit the reaction, which probably happens at the triple phase boundary, similar to a pure electronic conductor.