Combining La0.5Sr0.5MnO3-δ cathode with a mixed conductor towards enhanced performance of proton-conducting solid oxide fuel cells

[Display omitted] •The traditional LSM was coupled with BSIF as a cathode for H-SOFCs.•An apparent synergistic effect was discovered, boosting the performance.•High fuel cell performance was obtained with the LSM + BSIF cathode.•The mechanism for the enhanced cathode performance was revealed. Exploring high-performance cathodes is critical for proton-conducting solid oxide fuel cells (H-SOFCs), as they significantly impact cell performance at intermediate temperatures. Traditional cathodes may also be an attractive option due to their established practicality in practical applications, assuming their cathode catalytic activity can be increased. Traditional Sr-doped LaMnO3 (LSM), one of the most successful cathodes in the community, can only function well at high temperatures, and its performance in H-SOFCs is inadequate. Although using a composite cathode, in which the LSM is coupled with a proton-conducting electrolyte material, typically LSM + BaCe0.7Zr0.1Y0.2O3-δ (BCZY), can improve performance, it remains inferior to many newly produced cathodes, demonstrating insufficient competence. To address this issue, the mixed conductor BSIF, rather than a pure proton conductor, is utilized to pair LSM for the cathode composite. The BSIF mixed conductor has good thermal compatibility with LSM. Furthermore, the H-SOFC with the LSM + BSIF cathode performs better than fuel cells with LSM or BSIF cathodes. An apparent synergistic effect is discovered. The weight ratio of LSM and BSIF in the composite cathode impacts fuel cell performance, with the optimal composition being LSM (50 wt%) and BSIF (50 wt%). First-principles calculations show that the formation of LSM/BSIF alters the electronic structure of the material, increasing cathode ORR activities. The H-SOFC with the LSM (50 wt%) + BSIF (50 wt%) cathode produces a fuel cell output of 1615 mW cm−2 at 700 °C, which is much higher than that of the conventional LSM + BCZY composite cathode, which is only 725 mW cm−2. Furthermore, the LSM + BSIF provides better chemical stability than the traditional LSM + BCZY composite cathode, making LSM + BSIF a high-performing and robust cathode choice for H-SOFCs.