An excellent bismuth-doped perovskite cathode with high activity and CO2 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, Bi 0.15 Sr 0.85 Co 0.8 Fe 0.2 O 3−δ (BiSCF) is systematically evaluated as a carbon dioxide (CO 2 )-tolerant and highly active cathode for SOFCs. BiSCF, which features Bi 3+ with an ionic radius similar to Ba 2+ , exhibits activity (e.g., 0.062 Ω cm 2 at 700 °C) comparable to that of Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ and PrBaCo 2 O 5+δ , 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 −2 at 650 °C. The CO 2 -poisoned BiSCF exhibits quick reversibility or slight activation after returning to normal conditions. The exceptional CO 2 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.