Degradation Analysis of SOFC Stack Performance: Investigation of Cathode Sulfur Poisoning Due to Contamination in Air

Abstract

Central Research Institute of Electric power Industry (CRIEPI) has operated seven types of SOFC stacks, which are developed by MITSUBISHI HITACHI POWER SYSTEMS (MHPS), KYOCERA, TOTO, NGK SPARK PLUG (NTK), NGK INSULATORS (NGK), MURATA Manufacturing (Murata), and Denso in order to investigate their durability and find dominant degradation factor for each SOFC stacks under NEDO’s project. In the first half of period, remarkable feature of durability tests was large cathode degradation in KYOCERA’s, NGK’s, and Murata’s cells which were examined at CRIEPI site. Because sulfur was detected on their cathodes from post analyses done by AIST with SIMS, in the last half of period, these stacks were reexamined by adopting sophisticated chemical filter for SO2 removal. Results become more acceptable. On the other hands, SO2 concentration in air at CRIEPI site was less than 3 ppbv. The amount of sulfur detected on cathode is significantly larger than that of calculated sulfur from supplied air, another sulfur sources might be considered.