Component analysis of a 25-cell stack following 6.7 kh of high temperature electrolysis

Abstract

The demonstration of relevant lifetimes for solid oxide electrolysis stacks is an underlying necessity to the rapidly industrializing technology. Following a 6.7 kh test of a 25-cell stack, post-mortem analyses of cells, seals, and interconnects were carried out to assess their long-term stability.Micrographs of cells aged in nominal conditions highlighted Ni depletion in the functional layer, SZO interlayer growth, and the presence of a Sr-rich secondary phase. The microstructure of glass-ceramic seals remained for the most part stable following operation. In addition, in spite of a thin design and the absence of coating, interconnects showed remarkable stability, with limited chromia growth and Cr depletion. Notably, no Cr poisoning could be detected in the cell functional layer.In view of the results, the loss of tightness of the H2 compartment, due to initial defects or caused by failures, is seen as the most immediate threat to this stack long-term operation.