Strain-Regulated La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ for Sr Stable and CO₂-Tolerant Oxygen Electrode in Reversible Solid Oxide...

Reversible solid oxide cells (Re-SOCs) are promising devices for efficient energy conversion and CO₂ utilization. However, conventional La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) oxygen electrodes suffer from severe Sr surface segregation and CO₂ poisoning, which lead to the formation of insulating SrCO₃ 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 CO₂ 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 CO₂ 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 CO₂-tolerant electrodes in Re-SOCs.