Understanding the occurrence of the individual CO2 electrolysis during H2O-CO2 co-electrolysis in classic planar Ni-YSZ/YSZ/LSM-YSZ solid oxide cells

Abstract Commercialized Ni-YSZ/YSZ/LSM-YSZ solid oxide cells with the dimension of 10cm×10cm are investigated in the H 2 O-CO 2 co-electrolysis mode at 800°C. The aim is to understand the occurrence of the individual CO 2 electrolysis during polarization. The electrochemical impedance spectroscopy is combined with the online gas chromatography in order to reveal the possible processes. Several inlet gas flow scenarios are selected and tested at various current density. As a theoretical evidence, the electrolysis voltage comparison of H 2 O/H 2 and CO 2 /CO is presented as well. The results suggest the co-electrolysis process starts with the individual H 2 O electrolysis which has a relatively lower reaction barrier. The higher-reaction-barrier CO 2 electrolysis is activated and concurrent with the H 2 O electrolysis if more electric energy is applied and that’s when the real sense of H 2 O-CO 2 co-electrolysis occurs.