Effect of operating conditions on Molten Carbonate Electrolysis Cell performance: an experimental study

The study investigates the performance of a Molten Carbonate Electrolysis Cell (MCEC) under varying operational conditions, focusing on the interplay between electrochemical reactions and reverse water-gas shift (rWGS) reaction. Experimental tests were conducted using a MCEC single repeating unit (100 cm 2 active area), operating at different temperatures (620 °C, 650 °C, and 680 °C) and varying feed compositions of H 2 O and CO 2 (10 %, 20 %, 30 %, and 40 % molar fractions) at the fuel electrode. Electrochemical performance was evaluated through galvanostatic polarization and electrochemical impedance spectroscopy (EIS), while gas compositions were analyzed via gas chromatography to gain insights into the rate of reactions. Increasing operating temperature improves electrochemical performances while also enhancing the rWGS reaction, with a greater interplay between chemical and electrochemical processes. Higher CO 2 and H 2 O concentrations influenced both electrolysis and rWGS, affecting overall cell performance. Notably, limited CO 2 supply led to performance degradation, indicating its crucial role not only as a reactant in electrolysis but also in sustaining rWGS. The study also observed that excess CO 2 contributed to maintaining cell efficiency by promoting rWGS, supplementing H 2 production under water-limited conditions. Findings can contribute to better understand the interactions between temperature, gas composition, and reaction mechanisms in MCECs, offering possibilities for optimization. • MCEC tested under varying CO 2 and H 2 O concentrations at different temperatures. • Low CO 2 feeding enables pure H 2 production. • rWGS reaction identified as key mechanism under water-limited conditions. • Gas analysis confirms deviation from electrolysis-only predictions. • Thermodynamic model shows rWGS potential exceeds experimental conversion.