Ru‐Doping‐Induced Dual‐Functionality in La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3‐δ : Enhancing Efficient Multi‐Fuels Oxidation and Suppressing Sr Segregation for Robust Symmetric Solid Oxide Cells

Symmetric solid oxide cells (SSOCs) have attracted considerable attention because of their simplified architecture and reversible operation, but their advancement is hindered by a scarcity of electrode materials that simultaneously combine high catalytic activity and robust redox stability. Herein, B‐site Ru‐doped, A‐site‐deficient (La 0.6 Sr 0.4 ) 0.9 Ru 0.1 Co 0.2 Fe 0.8 O 3‐δ (LSRCF) is developed as a high‐performance symmetric electrode. Ru doping combined with A‑site deficiency enables dual functionality. On the fuel electrode side, CoFeRu nanoalloys exsolve in situ to form active metal/oxide heterointerfaces, accelerating fuel oxidation. DFT calculations further reveal that the exsolved CoFeRu/RP‐LSRCF heterointerface strengthens propane adsorption, lowers the dehydrogenation barrier, and facilitates oxidation of carbonaceous intermediates, thereby accounting for the excellent coking resistance. On the oxygen electrode side, Ru suppresses detrimental Sr segregation by increasing its migration barrier and improves oxygen reduction kinetics. At 850°C, the LSRCF cell delivers peak power densities of 940, 860, and 1230 mW cm −2 under H 2 , CH 4 , and C 3 H 8 , respectively, with outstanding tolerance to coking and sulfur. In CO 2 electrolysis mode, the cell achieves a current density of 3390 mA cm −2 at 1.6 V and 850°C with stable long‐term operation. These results demonstrate an effective strategy for developing high‐performance symmetric electrode materials.