Strain‐Regulated La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3‐δ for Sr Stable and CO ₂ ‐Tolerant Oxygen Electrode in Reversible Solid Oxide Cells

ABSTRACT Reversible solid oxide cells (Re‐SOCs) are promising devices for efficient energy conversion and CO 2 utilization. However, conventional La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3‐δ (LSCF) oxygen electrodes suffer from severe Sr surface segregation and CO 2 poisoning, which lead to the formation of insulating SrCO 3 and rapid performance degradation. Herein, an ordered macroporous LSCF oxygen electrode (LSCF@PMMA) is constructed via a template‐assisted strategy to regulate lattice strain and surface stability. The macroporous architecture introduces compressive lattice strain and well‐defined mass‐transport channels, which enlarge the triple‐phase boundaries (TPBs). Structural analyses and detailed theoretical calculations reveal that the strain‐enhanced O‐2p‐M‐3d hybridization lowers the energy barriers for oxygen adsorption and dissociation while increasing the Sr migration barrier. Time‐of‐Flight Secondary Ion Mass Spectrometry (TOF‐SIMS) and in situ Raman further verify that suppressed Sr segregation effectively enhances CO 2 tolerance. As a result, the single‐cell with the LSCF@PMMA electrode delivers a peak power density of 1.22 W cm −2 at 850°C in fuel cell (FC) mode and a current density of 3.35 A cm −2 at 1.8 V for CO 2 electrolysis, while also exhibiting negligible degradation over 150 h in FC mode and excellent stability during reversible operation. This work highlights strain‐engineered as an effective strategy for developing intermediate‐temperature CO 2 ‐tolerant electrodes in Re‐SOCs.