A study of cathode materials for intermediate temperature SOFCs prepared by the sol-gel method

We fabricated cells with La0.8Sr0.2MnO3 (LSM) cathodes impregnated with catalytically active perovskite type materials after sintering the cathodes on Sc2O3- and Al2O3-doped zirconia electrolyte by the sol-gel method. We found that the overpotential of the LSM cathodes at 700 °C was reduced by half or more by impregnating it with La0.5Sr0.5CoO3 (LSCO), LaCoO3 (LCO) or LaNi0.6Fe0.4O3 (LNF). AC impedance measurements showed that the triple phase boundary (TPB) of the cathodes was significantly increased by the impregnation. However, if we are to apply this method to SOFC cathodes at 800 °C, the impregnating materials must be limited to relatively stable materials such as LCO or LNF to avoid a reaction with the zirconia electrolyte or an LSM cathode.