Stability of an A-Site Deficient (La0.6Sr0.4)(Co0.2Fe0.8)O3–δ Oxygen Electrode and the Effect of Gd0.1Ce0.9O1.95 Compositing for Intermediate-Temperature Solid Oxide Electrolyzers

The electrochemical stability of oxygen electrodes is paramount for the sustainability and commercial viability of solid oxide electrolyzer (SOEC) technology. While the family of (La,Sr)(Co,Fe)O3–δ (LSCF) perovskites has been extensively studied, understanding regarding the stability for its A-site deficient variants—despite their growing practical interest for improved electrochemical and thermomechanical compatibility—remains scarce, particularly within the reduced temperature range where current commercialization efforts are heavily concentrated to enhance system economics. Here, we evaluate the degradation behavior of (La0.6Sr0.4)0.95(Co0.2Fe0.8)O3–δ (A-LS) at 600℃ and 650℃ and assess the impact of Gd0.1Ce0.9O1.95 (GDC) compositing, a common strategy for kinetic enhancement. Symmetric cells were employed to probe electrode polarization evolution via electrochemical impedance spectroscopy, with changes in individual processes resolved using equivalent-circuit model-based simulation and subtractive impedance analysis. Post-test X-ray photoelectron spectroscopy, X-ray diffraction, and Scanning electron microscope measurements corroborate the electrochemical findings. The results reveal that A-LS exhibits progressive surface deactivation driven by Sr segregation, which intensifies at reduced temperature and ultimately leads to electrode–electrolyte delamination in SOEC mode. In contrast, GDC compositing substantially mitigates these degradation pathways, preserving interfacial stability and demonstrating its efficacy in ensuring the mechanical and electrochemical integrity of LSCF-based electrodes for intermediate-temperature SOECs.