Effect of H_2O and CO_2 on LSCF-GDC Composite Cathodes

摘要

Polarization losses associated with the cathode oxygen reduction reaction (ORR) and degradation of cathode materials remain as hurdles for widespread implementation of solid oxide fuel cells (SOFC). Rates of degradation depend significantly on the operating temperature and gas conditions, such as the presence of unwanted oxygen-containing compounds, namely H_2O and CO_2. In this study, we explore H_2O and CO_2 degradation mechanisms for a common composite cathode material, La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ) (LSCF) - Ce_(0.90)Gd_(0.10)O_(1.95) (GDC) using electrochemical impedance spectroscopy (EIS) under various temperatures, oxygen partial pressure, and contaminant conditions to determine the effect of H_2O and CO_2 on LSCF-GDC. Our results suggest that CO_2 and H_2O compete with the ORR, and a strong correlation between blocking, degradation, and sintering effects caused by CO_2 and H_2O is directly observed. The interactions of CO_2 and H_2O with the cathode surface changes as a function of operating temperature, resulting in different short-term or long-term degradation mechanisms.