Degradation of flat-tube solid oxide electrolytic stack for co-electrolysis of H2O and CO2 under pulsed current

Abstract

The coupling of CO2 electrolysis and renewable energy storage is of great significance, especially to CO2 capture and utilization. In this work, the factors influencing the performance and degradation of flat-tube solid oxide electrolytic cell stack (SOEC stack) for CO2/H2O co-electrolysis under an intermittent pulsed current are investigated by inserting a voltage lead inside the SOEC stack to monitor the variations in the cell and stack voltages during the electrolysis process. The results show that after 64 pulsed electrolysis cycles (900 h), the average voltage degradation rate is about 0.018%/cycle at 50–250 mA/cm2, and the useful life is expected to reach more than 1100 cycles (10,000 h). The microstructural analysis shows that a SrCrO4 barrier layer is formed on the contact surface between the metal interconnect and the current collecting layer of the cell, which increases the interface resistance of the metal interconnect and the cell, resulting in the degradation of the electrolytic performance. This study provides useful information for improving the stability of the SOEC stack for CO2/H2O co-electrolysis.