Degradation Mechanism of SOFC Cathodes under CrO3and SO2Impurity Exposures

The effects of Cr-and S-impurities on the cathode performances were examined at the mixed ionic-electronic conducting La0.6Sr0.4Co0.2Fe0.8O3(LSCF) cathode. Under exposures to CrO3and SO2, the cathode performance decreased drastically by forming SrCrO4and SrSO4at the LSCF grain surfaces and electrochemical active sites. The main degradation factors of LSCF cathode was the decrease of surface reaction rates by the impurities. The Sr-diffusion and depletion in the LSCF structures can affect the cathode performance degradation. Relatively large amounts of Sr were depleted in the LSCF grains under CrO3exposures by forming a thick SrCrO4at the Pt-mesh/LSCF cathode interfaces, while small amounts of Sr-depletion in the LSCF grains under SO2exposures.