Mechanistic Study on the Corrosion of (La,Sr)(Co,Fe)O_3-δ Cathodes Induced by CO₂

Solid Oxide Fuel Cell (SOFC) cathodes operating in ambient atmospheric conditions inevitably encounter CO₂ contamination, leading to sustained performance deterioration. In this investigation, we examined the impact of CO₂ on three variants of (La,Sr)(Co,Fe)O_3-δ cathodes and employed the distribution of relaxation times method to distinguish distinct electrochemical processes based on impedance spectra analysis. We meticulously analyzed and discussed the corrosion resistance of these (La,Sr)(Co,Fe)O_3-δ cathodes under high CO₂ concentrations, relying on the experimental data. Electrochemical impedance spectroscopy results revealed that La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF-6428), La_0.4Sr_0.6Co_0.2Fe_0.8O_3-δ (LSCF-4628), and La_0.4Sr_0.6Co_0.2Fe_0.7Nb_0.1O_3-δ (LSCFN-46271) cathodes exhibited persistent degradation when exposed to CO₂ at temperatures of 650 °C or 800 °C during the durability-testing period. An increase in electrode polarization resistance was observed upon CO₂ introduction to the electrode, but electrode performance recovered upon returning to a pure air environment. Furthermore, X-ray diffraction and scanning electron microscopy analyses confirmed that CO₂ did not cause permanent damage to the (La,Sr)(Co,Fe)O_3-δ cathodes. These findings indicate that the (La,Sr)(Co,Fe)O_3-δ cathodes exhibit excellent resistance to CO₂-induced corrosion.