Accelerated Degradation of SOFC Cathodes by Cr Vapors

Among the degradation factors of SOFCs, Cr poisoning is one of the important issues for long-term operation. Pre-oxidized Cr metal was used to generate Cr vapors to accelerate Cr poisoning at cathodes. Cathodic polarization currents decrease with time due to deposition of Cr at electrochemical active sites. The concentration levels of Cr in the porous cathodes (La0.8Sr0.2MnO3 (LSM)) and La0.8Sr0.2FeO3 (LSF)) were determined by secondary ion mass spectrometry (SIMS). The concentration level of Cr changes from 100 to 2000 ppm depending on cathode materials and analyzed areas. For LSM cathode, a maximum of Cr concentration was observed at the LSM/electrolyte interface, while no condensation was observed at the LSF/electrolyte interface. The concentration of Cr deposited in the LSF cathode is estimated to be about 21-25% of the supplied Cr and is about 1.8 times higher than the concentration of Cr atoms in the LSM. The electrochemical performance of LSF is relatively high compared with that of LSM.