A Highly Efficient and Robust Bifunctional Perovskite‐Type Air Electrode with Triple‐Conducting Behavior for Low‐Temperature Solid Oxide Fuel Cells

Abstract Cobalt‐rich materials have generally been recognized as the prevailing candidates of cathodes for low‐temperature solid oxide fuel cells (LT‐SOFCs, 400–600 °C). Regrettably, their instability and high cost are the major concerns for future commercialization. In response to these drawbacks, here, an A‐site‐deficient low‐cobalt‐containing perovskite‐type oxide, Ba 0.95 Fe 0.7 Co 0.2 Sc 0.1 O 3‐δ (BFCS0.95), as an efficient bifunctional electrode with triple‐conducting (H + |O 2− |e − ) nature for oxygen‐ion conducting SOFCs (O‐SOFCs) and proton conducting SOFCs (H‐SOFCs) is proposed. BFCS0.95 electrode exhibits impressive versatility in catalyzing oxygen reduction reaction, i.e., ultralow area‐specific resistances (0.072 Ω cm 2 for O‐SOFCs and 0.4 Ω cm 2 for H‐SOFCs at 550 °C, respectively), extraordinarily high power outputs (1092 mW cm −2 for O‐SOFCs and 419 mW cm −2 for H‐SOFCs at 550 °C, respectively), excellent long‐term durability (>100 h for O‐SOFCs and H‐SOFCs at 600 °C), remarkable reversibility between pure air and CO 2 ‐containing air, and superior resistance against temperature fluctuations. The combined experimental and computational studies elucidate the roles of A‐site deficient state and triple‐conducting behavior, both of which are essential to overall electrochemical performance. Low‐cobalt‐containing feature also makes BFCS0.95 cathode economically competitive among all cobalt‐containing analogues. Overall, the finding paves a highly efficient route to develop bifunctional electrodes for LT‐SOFCs toward a sustainable energy future.