A-site doping enabled synergistic regulation of phase transition and electron spin state for improved performance of La _0.6 Ca _0.4 FeO _{3− <i>δ</i>} cathodes in solid oxide fuel cells

Although intermediate temperature solid oxide fuel cells (IT-SOFCs) show great potential to address energy conversion challenges, the sluggish oxygen reduction reaction (ORR) kinetics of cathode materials has severely hindered extended applications. Herein, we demonstrated that Bi³⁺ doping on the A-site synergistically regulates the phase transition and electron spin state in La_0.3Bi_0.3Ca_0.4FeO_3-δ (LBCF3) for improved performance. An orthorhombic to cubic phase transition occurred with Bi³⁺ doping increases oxygen vacancy concentration and thus increased oxygen ion migration capacity. Simultaneously, the change of Fe from low to medium electron spin state strengths O₂ adsorption and improves catalytic performances. Consequently, up to 48% (from 1.21 to 1.79 W·cm^-2) peak power density improvement at 800 °C is realized in the anode-supported single cell using LBCF3 as cathode, which remains stable for over 270 h at 750 °C