A Study of SOFC Cathode Degradation in H2O Environments

An understanding of the degradation mechanisms of SOFC cathodes under operating conditions is essential for the development of commercial, low temperature (<700°C) SOFCs with high performance. Literature shows that the presence of H₂O in the cathode impacts the performance of SOFCs. In this study, we attempt to determine the degradation mechanisms of two SOFC cathodes ((La_0.8Sr_0.2)_0.95MnO_3-x (LSM) and La_0.6Sr_0.4Co_0.2Fe_0.8O_3-x (LSCF)) in H₂O based on a multi-faceted approach. LSM-YSZ/YSZ/LSM-YSZ and LSCF-GDC/GDC/LSCF-GDC symmetric cells will be examined in the presence of the contaminant (H₂O) under different cycling, polarization and working conditions. Symmetric cell performance will be measured by in-situ electrochemical impedance spectrometry (EIS), and directly compared to quantitative microstructural parameters obtained from FIB-SEM 3D reconstructions. FIB-SEM is a powerful technique that can help us visualize the complex cathode/electrolyte microstructure, and allow us to quantify important performance characteristics such as triple phase boundary (TPB) length and surface to volume ratio. EIS and FIB-SEM results will then be compared to kinetic rate data, determined by isotope exchange experiments, to determine correlations.