An excellent bismuth-doped perovskite cathode with high activity and CO₂ resistance for solid-oxide fuel cells...

Lowering the operating temperatures of solid-oxide fuel cells (SOFCs) is critical, although achieving success in this endeavor has proven challenging. Herein, Bi_0.15Sr_0.85Co_0.8Fe_0.2O_3-δ (BiSCF) is systematically evaluated as a carbon dioxide (CO₂)-tolerant and highly active cathode for SOFCs. BiSCF, which features Bi³⁺ with an ionic radius similar to Ba²⁺, exhibits activity (e.g., 0.062 Ω cm² at 700 °C) comparable to that of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ and PrBaCo₂O_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 CO₂-poisoned BiSCF exhibits quick reversibility or slight activation after returning to normal conditions. The exceptional CO₂ 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.