The spatiotemporal evolution process study on performance degradation of solid oxide fuel cell induced by carbon deposition

Abstract

The cell durability issue induced by carbon deposition is a developmental obstacle for commercial SOFCs. A dynamic carbon-deposition model of SOFC with detailed structures is developed in this work to explore the spatiotemporal evolution process of cell degradation. Both porosity and reaction activity dominate the cell degradation and their spatiotemporal evolution discrepancies can weaken the cell high current density regions. There are pronounced degradation differences along the flow direction, which will be magnified over time. During the operation, the porosity is reduced by about 30%; the reaction activity is reduced by more than 20% and their spatial differences reach up to 9.60% and 8.07%, respectively. For cell structures, counter-flow configuration performs better in terms of thermal stress and cell durability; the effect of increasing anode thickness on mitigating carbon deposition gradually diminishes; appropriately increasing the through-hole spacing and fluid distribution chamber size can significantly improve the spatial inhomogeneity of cell degradation. Regarding operating conditions, the degradation rate at steam-to-carbon ratio (S/C) = 0.79 is 4.27% higher than that at S/C = 2.88; the carbon deposition degree varies oppositely under various operating potentials due to the competition among different reactions. A high fuel utilization factor can help alleviate cell degradation induced by carbon deposition. The current density of the larger S/C may exceed that under other S/C conditions. Reducing the operating temperature can extend this “exceeding behavior” by about 760 h.