Interrelation between Sulfur Poisoning and Performance Degradation of LSCF Cathode for SOFCs

Performance degradation of SOFC cathodes has been partly attributed to sulfur dioxide (SO 2 ), which is one of the major impurities naturally present in air. In this work, the sulfur poisoning behavior of (LaSr)(CoFe)O 3 (LSCF) cathodes exposed to 1 ppm of SO 2 in air was investigated as a function of time under various operation temperatures of 923 K, 973 K, and 1073 K. Severe performance degradation was observed at low temperatures of 923 K and 973 K. For these cases, only the polarization resistance ( R p ) was increased, additionally no sulfur component was detected in the LSCF cathode. At 1073 K, both R p and ohmic resistance ( R ohmic ) increased during the progress of degradation and SrSO 4 was observed in cathode, especially near the LSCF/GDC interface. Plausible sulfur poisoning mechanisms were proposed based on the observed experimental phenomena.