Long-term evaluation of solid oxide fuel cell candidate materials in a 3-cell generic short stack fixture, part Ⅰ: Test fixture, sealing, and electrochemical performance

摘要

A generic solid oxide fuel cell stack test fixture was developed to evaluate candidate materials and processing under realistic conditions. A NiO-YSZ anode-supported YSZ electrolyte cell with a composite cathode was used to evaluate the long-term stability of a sealing system, alumina coating, Ce-modified (Mn,Co)-spinel coating, ferritic stainles steel AISI441 interconnect metal, and current collectors. A 3-cell short stack was assembled and tested in constant current mode for 6000 h at 800 ℃. Part Ⅰ of the work addresses the stack fixture design, cell components, sealing system, cell performance, and post-mortem analysis. Parts Ⅱ and Ⅲ will discuss microstructure evolution, interfacial reactions, and degradation mechanisms. During 6000 h of testing, the top cell showed very low degradation (～ 1.4% kh~(-1)), while the middle and bottom cells exhibited much higher degradation after ～2000 h. The rapid cell degradation was correlated to the open circuit voltage measurements and was attributed to glass seal failure, probably due to unbalanced stress conditions. Post-mortem analysis showed a characteristic yellowish color around the glass seal, suggesting formation of SrCrO_4. Overall the developed stack test fixture was demonstrated as a simple and useful tool for evaluation of SOFC candidate materials in realistic conditions.