Syngas production on a symmetrical solid oxide H2O/CO2 co-electrolysis cell with Sr2Fe1.5Mo0.5O6–Sm0.2Ce0.8O1.9 electrodes

• SFM is a promising alternative electrode for the solid oxide co-electrolysis cell.
• The co-electrolysis cells show a current density of −734 mAcm−2 at 850 °C.
• Syngas with CO2 conversion rate of 0.58 and H2 to CO ratio of 2 has been achieved.
• Gas fraction evolution for co-electrolysis process are predicted by the chemical equilibrium model.

High temperature H2O/CO2 co-electrolysis process is performed on the symmetrical Sr2Fe1.5Mo0.5O6(SFM)-Sm0.2Ce0.8O1.9(SDC)/La0.8Sr0.2Ga0.87Mg0.13O3 (LSGM)/SFM-SDC cells, which exhibit excellent electrochemical performance with the current density of −734 mAcm−2 at 1.3 V and the interfacial polarization resistance of 0.48 Ωcm2 at 850 °C. Enhanced co-electrolysis kinetics are obtained with increasing the operating temperature and applied cell voltage. Synthesis gas of H2 and CO is produced by H2O splitting and reverse water gas shift (RWGS) reaction on the SFM-SDC/LSGM/SFM-SDC co-electrolysis cells. Effects of temperature and electrolysis current on the produced gas fraction are predicted using the chemical equilibrium co-electrolysis model. High CO2 conversion rate and ideal H2 to CO ratio of approximately 2 can be achieved by adjusting appropriate inlet gas fraction, temperature and electrolysis current. The SFM-SDC/LSGM/SFM-SDC cell shows a relative stable cell voltage in the 103-h galvanostatic test.