Accelerated Degradation of SOFC Cathodes by Cr Vapors

Abstract

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