Performance of CO<sub>2</sub>/H<sub>2</sub>O Co-electrolysis in a Flat-tube Solid Oxide Electrolysis Cell Stack under Air-free Environment

This work investigates the transient performance and stability of CO2/H2O co-electrolysis in an air-free environment using a flat-tube solid oxide electrolysis cell (SOEC) stack. The results show that the transient behavior of the stack with and without blowing gas in the air electrode is almost the same. With a current density of 0.67 A·cm−2@750 °C, the stack operated for over 200 h under co-electrolysis conditions with no air blowing, and the voltage drop rate of the stack was approximately 0.203%/100 hours. Microstructure analysis reveals significant loss of Ni particles and formation of an insulating phase SrCrO4 on the surface of the current collection layer of the air electrode, which are identified as key factors contributing to performance degradation of the stack. This study provides a reference for efficient fuel preparation technology based on SOEC stack in airless environments.