Study on the long-term discharge and redox stability of symmetric flat-tube solid oxide fuel cells

In this work, we investigated the stabilities of a newly developed symmetric flat-tube solid oxide fuel cells with double-sided cathodes (DSC cells) for long-term discharge and redox cycling operations. The DSC cell was discharged at 750°Cusing pure H₂ fuel for ca. 2030 h and the degradation rate was ca. 10% per one thousand hours. In addition, H₂ and air were alternatively supplied to the anode of DSC cells for tens of cycles in order to investigate the redox-stability. The duration time of oxidation process was found to be dominant for the stability of the cell. The microstructure of the DSC cells before and after these tests were investigated in order to clarify the degradation mechanisms. A great number of Ni particles with a diameter of ca. 2 μm was exsolved in the large pores of anode support layer after the redox cycling test with long duration time of oxidation. Such phenomenon induced by redox cycling has not been reported in the literatures. Based on the experimental data, the mechanisms were discussed.