Infiltration, Overpotential and Ageing Effects on Cathodes for Solid Oxide Fuel Cells: La0.6Sr0.4Co0.2Fe0.8O3-delta versus Ba0.5Sr0.5Co0.8Fe0.2O3-delta

La0.6Sr0.4Co0.2Fe0.8O3-? (LSCF) and Ba0.5Sr0.5Co0.8Fe0.2O3-? (BSCF) cathode powders were obtained from solution combustion synthesis, deposited onto Ce0.8Sm0.2O2-? electrolytes and eventually infiltrated with a La0.8Sr0.2MnO3-? (LSM) nanosized discrete layer. The two half-cell systems were compared to evaluate the influence of infiltration, overpotential and ageing on their performance and stability. Structure, microstructure and chemical composition were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with Energy Dispersive X-ray spectroscopy (EDX), whereas redox behavior was evaluated through temperature programmed reduction (TPR) and thermal gravimetric analysis (TGA) in combination with electrochemical impedance spectroscopy (EIS), which was also used to test the electrochemical performance. A decrease of polarization resistance for both infiltrated electrodes, compared to the reference ones, was highlighted at open circuit voltage (OCV), although the BSCF-based cathode was more benefitted more from infiltration than the LSCF-based one. Moreover, the application of cathodic overpotentials (-0.1 to -0.3 V) resulted in opposite effects on the LSCF- and BSCF-based cathodes, highlighting a different response of the oxygen vacancies to the applied voltage for the two perovskite compositions. The positive effect of the LSM layer was further confirmed by the observed improvement in long-term stability of both infiltrated perovskite-type systems.