Synthesis, characterization and evaluation of PrBaCo2−xFexO5+δ as cathodes for intermediate-temperature solid oxide fuel cells

Iron doped layered structured perovskites, PrBaCo2−xFexO5+δ (x = 0, 0.5, 1.0, 1.5 and 2.0), are evaluated as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The effects of dopant content are investigated on their structural and electrochemical properties including crystalline structure, oxygen nonstoichiometry, stability in presence of CO2, compatibility with electrolytes, thermal expansion coefficient, electrical conductivity, and cathodic interfacial polarization resistance. The lattice parameter and oxygen nonstoichiometry content, δ, at room temperature increase, whereas the conductivity, thermal expansion coefficient, and cathodic performance decrease with increasing iron content, x. PrBaCo2−xFexO5+δ exhibit excellent stability at 700 °C in atmosphere consisting of 3% CO2 and 97% air, show good chemical compatibility with doped ceria electrolytes at 1000 °C, but react readily with yttria-stabilized zirconia at 700 °C. Even with a Co-free PrBaFe2O5+δ as the electrode, a symmetrical cell demonstrates area specific resistance of 0.18 Ω cm2 at 700 °C with samaria-doped ceria electrolyte. The resistance is lower than those for typical Co-free electrodes reported in the literatures, suggesting that PrBaCo2−xFexO5+δ are potential promising cathode materials for IT-SOFCs.

Research highlights► PrBaCo2-xFexO5+δ is pretty stable under atmosphere containing 3% CO2, and the stability is not affected by Fe content. ► Iron doping of PrBaCo2-xFexO5+δ is effective to reduce the thermal expansion coefficient, which is beneficial for SOFC systems in maintaining long-term stability and enduring thermal cycle. ► Even with a Co-free PrBaFe2O5+δ as the electrode, the resistance is lower than those for typical Co-free electrodes reported in the literatures, suggesting that PrBaCo2-xFexO5+δ are potential promising cathode materials for IT-SOFC.