Modification of surface chemistry of LSCF and BSCF electrodes through LSM infiltration

La1-xSrxCoyFe1-yO3-? (LSCF) and Ba1-xSrxCo1-yFeyO3-? (BSCF) perovskites have been widely studied as cathode materials for solid oxide fuel cells (SOFCs) because of their recognized excellent activity for oxygen reduction at intermediate temperatures (873 - 973 K). For LSCF, the Sr migration towards interfaces has been found as one of the main causes of degradation during long-lasting runs. Regarding BSCF, it shows the best activity towards oxygen reduction among the known perovskite oxides, but it suffers from a much more pronounced lattice instability (with respect to LSCF), leading to slow partial trasformation to other perovskites, especially an inactive hexagonal phase, after prolounged thermal treatment at intemediate temperatures (SOFC operating conditions). Moreover, BSCF is susceptible to CO2 ambient contamination, forming Sr and Ba carbonates. In this study, an La0.8Sr0.2MnO3-? (LSM) nanosized discrete layer (10 nm) has been infiltrated on La0.6Sr0.4Co0.2Fe0.8O3-? (LSCF6428) and Ba0.5Sr0.5Co0.8Fe0.2O3-? (BSCF5582) cathode backbones, deposited on Ce0.8Sm0.2O2-? (SDC20) electrolytes. A comparison of the two systems has been carried out by impedance spectroscopy at 973 K, to observe how LSCF and BSCF behave over time in terms of oxygen reduction activity (polarisation resistance) and chemical stability. The effectiveness of the infiltration in the inhibition of Sr segregation on LSCF surface is demonstrated after a 220 h ageing test (D.C. cathodic current of 200 mA cm-2) by EDS analyses. No carbonate formation is identified on the BSCF surface, anyway second phases have been observed after 800 h of ageing. LSM nanoparticles enhance the electrocatalytic activity at open circuit voltage for both LSM-impregnated LSCF and BSCF cathodes, due to the increase of the oxygen exchange surface. Moreover, in LSCF system LSM infiltration produces an improvement of the overall oxygen reduction activity, over the considered working time (220 h). In turn, the effect of LSM impregnation on BSCF cathode results in an inhibition of the electrode degradation in comparison with the reference BSCF cathode. The Cchem (chemical capacitance) has been extrapolated from the impedance measurements as a valuable method to investigate oxygen stoichiometric changes in the bulk of the electrodic materials. The trend of Cchem as a function of increasing cathodic overpotential shows that the oxygen vacancies concentration increases in LSCF while decreases in BSCF.