Positive effects of calcium-doping on the cathode performance of layered perovskite Eu1-xCaxBaCo2O5+δ for intermediate-temperature solid oxide fuel cells

Abstract A stable cathode with high catalytic activity toward oxygen reduction reaction (ORR) plays a key role in the commercialization of solid oxide fuel cells (SOFCs). Herein a series of layered perovskite oxides, Eu 1- x Ca x BaCo 2 O 5+ δ ( x  = 0–0.2), are synthesized and systematically evaluated as potential cathode materials for intermediate-temperature SOFCs (IT-SOFCs). The positive effects of calcium-doping on the cathode performance are confirmed by means of electrical conductivity, dilatometric and electrochemical measurements. The Ca-doping not only effectively optimizes the thermal expansion behavior but also significantly enhances the electrical conductivity. Among all of compositions, the Eu 0.8 Ca 0.2 BaCo 2 O 5+ δ sample exhibits the best catalytic ORR activity, as evidenced by a low area-specific resistance of 0.028 Ω cm 2 at 700 °C. A single cell with the Eu 0.8 Ca 0.2 BaCo 2 O 5+ δ cathode delivers a maximum power density of 1210 mW cm −2 at 700 °C, and can be steadily operated over a period of 100 h at a constant voltage of 0.5 V. These results demonstrate their promising application as cathode candidates for IT-SOFCs.