Evaluation of a brownmillerite oxide as cathode for solid oxide fuel cells

Brownmillerite oxide Ca2Fe1.3Mn0.7O5+δ is synthesized and evaluated as a new cathode material for solid oxide fuel cells (SOFCs). The average thermal expansion coefficient (TEC) of Ca2Fe1.3Mn0.7O5+δ is 13.3 ± 0.2 × 10−6 K−1, close to that of the typical electrolyte materials. The lowest polarization resistance (Rp) (0.22 ± 0.02 Ω cm2 at 750 °C in air) and cathodic overpotential values are achieved when the material is sintered at 1000 °C on Ce0.9Gd0.1O1.95 (CGO) electrolyte. Two main oxygen reduction reaction (ORR) processes are identified. The rate limiting step for ORR is found to depend on the oxygen partial pressure. The excellent electrochemical performance indicates that Ca2Fe1.3Mn0.7O5+δ can be a promising cathode material for SOFCs.

► Ca2Fe1.3Mn0.7O5+δ cathode material is studied for applications in SOFCs.
► Cathode material gave the lowest polarization resistance of 0.22 Ω cm2 at 750 °C.
► The rate limiting step for ORR depends on the oxygen partial pressure.