SmBa0.5Sr0.5Cu2O5+δ and SmBa0.5Sr0.5CuFeO5+δ layered perovskite oxides as cathodes for IT-SOFCs

Novel Cobalt-free layered perovskite oxides SmBa0.5Sr0.5Cu2O5+δ (SBSCO) and SmBa0.5Sr0.5CuFeO5+δ (SBSCFO) were investigated as cathode materials for intermediate-temperature solid fuel cells (IT-SOFCs). The thermal expansion coefficients (TEC) of SBSCO and SBSCFO were 14.1 × 10−6/°C and 14.9 × 10−6/°C in 50 °C–800 °C, which were more compatible with electrolyte than cobalt-based cathodes. When A′-site is partially substituted by Sr, the conductivity of SBSCO and SBSCFO had been improved. The max electrical conductivity of SBSCO was 277.7 S cm−1, about one order of magnitude higher than SmBaCu2O5+δ. Polarization resistance of SBSCO is 0.25 Ω cm2 at 650 °C, which is twice lower than that of SmBaCu2O5+δ (SBCO). This implies SBSCO has higher activity for oxygen reduction than SBCO. Preliminary results indicate that SBSCO are promising as cathodes for IT-SOFCs.