An excellent bismuth-doped perovskite cathode with high activity and CO resistance for solid-oxide fuel cells operating below 700 °C.

Lowering the operating temperatures of solid-oxide fuel cells (SOFCs) is critical, although achieving success in this endeavor has proven challenging. Herein, BiSrCoFeO (BiSCF) is systematically evaluated as a carbon dioxide (CO)-tolerant and highly active cathode for SOFCs. BiSCF, which features Bi with an ionic radius similar to Ba, exhibits activity (e.g., 0.062 Ω cm at 700 °C) comparable to that of BaSrCoFeO and PrBaCoO, while demonstrating a considerable advantage over Bi-doped cathodes. Moreover, BiSCF exhibits long-term stability over a period of 500 h, and an anode-supported cell with BiSCF achieves a power density of 912 mW cm at 650 °C. The CO-poisoned BiSCF exhibits quick reversibility or slight activation after returning to normal conditions. The exceptional CO tolerance of BiSCF can be attributed to its reduced basicity and high electronegativity, which effectively restrict surface Sr diffusion and hinder subsequent carbonate formation. These findings highlight the substantial potential of BiSCF for SOFCs operating below 700 °C.