Boosting oxygen reduction activity and CO₂ resistance on bismuth ferrite-based perovskite cathode for low-temperature solid oxide fuel cells below 600 °C

Developing efficient and stable cathodes for low-temperature solid oxide fuel cells (LT-SOFCs) is of great importance for the practical commercialization. Herein, we propose a series of Sm-modified Bi_0.7−xSm_xSr_0.3FeO_3−δ perovskites as highly-active catalysts for LT-SOFCs. Sm doping can significantly enhance the electrocatalytic activity and chemical stability of cathode. At 600 °C, Bi_0.675Sm_0.025Sr_0.3FeO_3−δ (BSSF25) cathode has been found to be the optimum composition with a polarization resistance of 0.098 Ω cm², which is only around 22.8% of Bi_0.7Sr_0.3FeO_3−δ (BSF). A full cell utilizing BSSF25 displays an exceptional output density of 790 mW cm⁻², which can operate continuously over 100 h without obvious degradation. The remarkable electrochemical performance observed can be attributed to the improved O₂ transport kinetics, superior surface oxygen adsorption capacity, as well as O 2p band centers in close proximity to the Fermi level. Moreover, larger average bonding energy (ABE) and the presence of highly acidic Bi, Sm, and Fe ions restrict the adsorption of CO₂ on the cathode surface, resulting in excellent CO₂ resistivity. This work provides valuable guidance for systematic design of efficient and durable catalysts for LT-SOFCs.