A new oxygen reduction electrocatalyst of barium lanthanide cobaltate for composite cathodes of proton-conducting ceramic fuel cells

Abstract

This is the first report of the application of the barium lanthanide cobaltate of Ba₄Sr₂Sm₂Co₄O₁₅ (BSSC) as an oxygen reduction electrocatalyst of proton-conducting ceramic fuel cells. In this study, composite cathodes of Ba₄Sr₂Sm₂Co₄O₁₅–BaCe_0.5Pr_0.3Y_0.2O_3−δ (BSSC–BCPY) were developed by varying the mixing ratio. The BSSC–BCPY composite with the optimal composition exhibited a polarization resistance of 0.19 Ω cm², 0.31 Ω cm², and 0.59 Ω cm² at 600 °C, 550 °C, and 500 °C, respectively, for the symmetrical cell test in 3% humidified synthetic air. Its activation energy was evaluated to be 68.5 kJ mol⁻¹. In this composite system, BSSC appeared to serve as an active phase for the dissociative adsorption of oxygen. The operation of the anode-supported cell employing the optimized cathode was successfully demonstrated at 600 °C, and a maximum power density of 197 mW cm⁻² was achieved upon feeding synthetic air and humidified hydrogen to the cathode and anode, respectively. Finally, the chemical stability of the BSSC–BCPY composite in a CO₂-containing atmosphere was evaluated.