Thermally Engineered Defects and Surface Architecture for High‐Performance Reversible Solid Oxide Cells Air Electrode

ABSTRACT Reversible solid oxide cells (RSOCs) provide an efficient route for interconverting electricity and hydrogen fuels, but their performance is limited by sluggish oxygen electrocatalysis at the air electrode. La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3‐δ (LSCF) is the most technically mature air electrode material; nevertheless, its oxygen electrocatalytic activity and stability remain inadequate. Existing strategies generally rely on compositional modification and surface decoration, often at the expense of processing simplicity and scalability. Here, we establish thermal processing as a simple and scalable strategy to unlock the oxygen electrocatalytic potential of LSCF by coordinately regulating its defect chemistry and surface architecture. Lowering the calcination temperature from 1000 (LSCF1000) to 800°C (LSCF800) coordinately activates Co/Fe redox centers, enriches oxygen vacancies, and preserves a high‐area surface architecture, accelerating oxygen surface exchange and bulk transport, enhancing activity. Meanwhile, the lattice expansion and enlarged surface area in LSCF800 alleviate La 3+ /Sr 2+ elastic mismatch and local Sr accumulation, suppressing Sr segregation and enhancing stability. Consequently, the LSCF800 electrode exhibits a polarization resistance of 0.014 Ω cm 2 with a degradation rate of 0.057% h −1 at 700°C, below that of LSCF1000 (0.094 Ω cm 2 and 0.46% h −1 ). This work establishes thermal regulation as an effective route for developing high‐performance oxygen electrodes for RSOCs.