Degradation behavior under alternating constant-current/constant-voltage discharge for flat-tube solid oxide fuel cells inside stack

• Published in: International journal of hydrogen energy 2023-05, Vol.48 (46), p.17654-17663
• Main Authors: Han, Beibei, Tang, Yafei, Wang, Jianxin, Guan, Wanbing, Singhal, Subhash C.
• Format: Article
• Language: English
• Subjects: Constant current; Constant voltage; DC discharge; Degradation; Solid oxide fuel cell
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2023.01.253

An alternating constant-current (CC)/constant-voltage (CV) discharge for the optimal operation mode of solid oxide fuel cells (SOFCs) inside stack is carried out, and the degradation of SOFCs is discussed. The SOFCs are operated alternately in CC/CV mode for 985 h at 750 °C. The results show that the degradation rate of SOFCs first decreases and then increases in the CC/CV alternating operation mode. And the lowest degradation rate is 3.64%/100 h in the CV operation mode at ∼0.85 V, which is about one order of magnitude higher than the average degradation rate (0.36%/100 h) in the corresponding CC operation mode. The EIS analysis indicates that the ohmic resistance increases and the polarization resistance decreases after the CV operation mode, while the impedance change after CC discharge shows the opposite trend. •SOFCs were operated under alternating constant-current(CC)/constant-voltage(CV) mode for 985 h.•The power degradation rate in CV mode was about ten times larger than that in the alternating CC mode.•The Rs increased and Rp decreased in CV mode, while the resistance showed an opposite trend in CC mode.