Rational A‐Site Multi‐Cation Design Enables Durable Fe‐Based Perovskite Air Electrodes for Fast Oxygen Reduction

Although Pr 0.5 Ba 0.5 FeO 3–δ (PBF)‐based perovskite cathodes are prevalent for solid oxide fuel cells (SOFCs), their practical application is hindered by Ba 2+ surface segregation, causing structural degradation, and poor CO 2 tolerance. Here, Pr 1/6 La 1/6 Nd 1/6 Ba 1/6 Sr 1/6 Ca 1/6 FeO 3–δ (PLNBSCF) is synthesized through A‐site multi‐cation doping, which reduces the A‐site cation size mismatch, shortens the Fe–O bond, lowers the charge‐transfer energy, and promotes oxygen reduction reaction kinetics. In addition, the increased Ba 2+ vacancy formation energy and weakened surface CO 2 adsorption improve resistance to CO 2 poisoning. As a result, a PLNBSCF‐based SOFC operates stably for over 300 h with a 64% decreased polarization resistance (0.058 Ω cm 2 ) at 700 °C and a 72% improved peak power density (1.55 W cm −2 ) compared with those of 0.163 Ω cm 2 and 0.88 W cm −2 in PBF, respectively. These results show that local lattice strain regulation via multi‐cation doping provides an effective route for designing durable and high‐performance Fe‐based SOFC cathodes.