Ferrite-based perovskites as cathode materials for anode-supported solid oxide fuel cells

The properties and the applicability of iron- and cobalt-containing perovskites were evaluated as cathodes for solid oxide fuel cells (SOFCs) in comparison to state-of-the-art manganite-based perovskites. The materials examined were La1−x−ySrxCo0.2Fe0.8O3 − δ (x = 0.2 and 0.4; y = 0 − 0.05), La0.8Sr0.2FeO3 − δ, La0.7Ba0.3Co0.2Fe0.8O3 − δ and Ce0.05Sr0.95Co0.2Fe0.8O3 − δ. The main emphasis was placed on the electrochemical properties of the materials, which were investigated on planar anode-supported SOFCs with 8 mol% yttria-stabilised zirconia (8YSZ) electrolytes. An interlayer of the composition Ce0.8Gd0.2O2 − δ was placed between the electrolyte and the cathode to prevent undesired chemical reactions between the materials. The sintering temperatures of the cathodes were adapted for each of the materials to obtain similar microstructures. In comparison to the SOFCs with state-of-the-art manganite-based cathodes, SOFCs with La1 − x − ySrxCo0.2Fe0.8O3 − δ cathodes achieved much higher current densities. Small A-site deficiency and high strontium content had a particularly positive effect on cell performance. The measured current densities of cells with these cathodes were as high as 1.76 A/cm2 at 800 °C and 0.7 V, which is about twice the current density of cells with LSM/YSZ cathodes. SOFCs with La0.58Sr0.4Co0.2Fe0.8O3 − δ cathodes have been operated for more than 5000 h in endurance tests with a degradation of 1.0-1.5% per 1000 h.