Study of Detailed Degradation Behavior of Solid Oxide Electrolyzer Cells (SOEC)

Kurzfassung

High temperature electrolysis has a high potential for the efficient production of hydrogen or syngas. For a further development of this promising technology, development work on materials and cells as well as extensive operational experience is still needed. A main objective is the improvement of the degradation behavior by elucidating the relevant degradation mechanisms. Cathode-supported cells were fabricated by ceramic processing and sintering for electrochemical characterization in electrolysis operating mode. For a systematic investigation of the influence of the operating parameters temperature, fuel gas humidification and current density on SOEC long-term degradation a series of measurements over 1000 hours in the temperature range 750-850 °C with different fuel gas humidity (40-80 mol%) and different current densities between 0 and 1.5 A/cm2 has been performed. The progress of degradation was monitored in-operando approximately every 150 h by impedance spectroscopy. Results of electrochemical cell characterization are shown and observed degradation phenomena and their underlying mechanisms based on different electrochemical processes are explained. Post-mortem investigations have been conducted to localize and identify the rate limiting processes and to clarify the correlation between degradation processes and operational parameters.