Electrochemical performance and durability of flat-tube solid oxide electrolysis cells for H2O/CO2 co-electrolysis

Abstract

Co-electrolysis of H2O and CO2 by high-temperature solid oxide electrolysis cells (SOECs) is a useful approach for energy storage and carbon dioxide reduction. In this study, we conducted H2O/CO2 co-electrolysis using a flat-tube SOEC and studied its electrochemical performance and durability. It was found that the increase of temperature and water fraction in fuel gas promote electrochemical performance. In addition, the co-electrolysis was found to be stable with a constant current density of 300 mA cm−2 for over 1000 h at 750 °C. The contribution of each electrode process to polarization resistance is elucidated by electrochemical impedance spectroscopy and distribution of relaxation time (DRT) analysis. The fuel electrode was found to degrade more significantly against duration time as compared to the oxygen electrode. Post-mortem analysis of the microstructure revealed the loss and sintering of Ni particles in active cathode functional layer at the inlet of the fuel electrode. Based on these results, the degradation mechanism of H2O/CO2 co-electrolysis by the flat-tube SOEC was discussed in details.