High-performance composite cathodes with tailored mixed conductivity for intermediate temperature solid oxide fuel cells using proton conducting electrolytes

A new composite cathode material made of La0.6Sr0.4Co0.2Fe0.8O3 - delta (LSCF), a mixed oxygen-ion/electron conductor, and BaZro(0.5)Pr(0.3)Y(0.2)O(3 - delta) (BZPY30), a mixed proton/electron conductor, is here developed for application in intermediate temperature solid oxide fuel cells (IT-SOFCs) based on proton conducting electrolytes. The wet chemical synthesis route allows sub-micrometre particle powders to be obtained, resulting in a highly porous microstructure. The developed composite cathode shows improved performance compared to the reported cathodes working in protonic SOFCs, achieving a total area specific resistance (ASR) in wet O-2 of 0.011, 0.089, and 0.6 Omega cm(2) at 700, 600, and 500 degrees C, respectively. Electrochemical impedance spectroscopy measurements indicate that several processes contribute to the overall cathode resistance. Performing area specific resistance measurements at different po(2) values allows the correlation of the various semicircles observed in the LSCF-BZPY30 impedance plots to different cathode reaction processes, i.e. water formation, oxygen surface dissociation, and diffusion. Fuel cell tests confirm the good performance of the LSCF-BZPY30 cathode for proton conducting oxide electrolytes.