A Design Paradigm for Sr ₂ Fe _1.5 Mo _0.5 O _6‐δ Cathodes in SOECs: Tailoring B‐O Covalent Hybridization and Spin State Regulations for High Performance CO ₂ Electrolysis

ABSTRACT Sr 2 Fe 1 . 5 Mo 0 . 5 O 6 (SFM) has drawn attention in SOEC for its favorable ionic and electronic conductivity, yet its CO 2 electrolysis performance is limited by A‐site Sr segregation and insufficient catalytic activity. In this study, we put forward a solution strategy via the B‐O covalent hybridization and spin state regulations through Ga doping. The findings indicate that the Sr segregation resistance and catalytic activity are synergistically optimized. The performance of the single cell employing SFMGa 0.25 as cathode can attain 2.11 A·cm − 2 at 800°C and 1.5 V, signifying a 41% enhancement. Simultaneously, the long‐term stability is substantially improved, which can operate stably for over 220 h even under 0.8 A·cm −2 . Electronic structure characterizations reveal that the incorporation of Ga strengthens the covalent hybridization between Fe‐3 d and O‐2 p , and shifts the Fe 3 d and O 2 p band centers closer to the Fermi level, which notably promotes the formation of oxygen vacancies as well as the electronic and oxygen ion conductivity. Moreover, Ga doping also increases the proportion of high‐spin (HS) Fe 4+ species and vacant e g orbitals, facilitating the adsorption and reducibility of CO 2 molecule. Therefore, this study would offer a novel perspective for the rational design of high‐performance SOEC cathode materials in the future.