Formation of hydrogen from the CO–H2O system using porous Gd-doped ceria electrochemical cell with MnO cathode and Fe3O4 anode

• Water-gas shift reaction proceeded through a porous electrochemical cell.
• With increasing heating temperature, the fraction of hydrogen formed increased.
• MnO in the cathode and Fe3O4 in the anode worked as catalysts.
• Disproportion of CO into CO2 and solid carbon occurred in the anode at low temperatures.

This paper reports the outlet gas composition and phase change of electrodes during the CO–H2O reaction (CO + H2O → H2 + CO2) using an electrochemical cell with MnO–GDC (Gd-doped ceria: Ce0.8Gd0.2O1.9) cathode/porous GDC electrolyte/Fe3O4–GDC anode system. In the cathode, oxidation of MnO by H2O (3MnO + H2O → Mn3O4 + H2) and electrochemical reduction of Mn3O4 occurred (Mn3O4 + 2e− → 3MnO + O2−). In the anode, reduction of Fe3O4 by CO (Fe3O4 + CO → 3FeO + CO2) and electrochemical oxidation of FeO occurred (3FeO + O2− → Fe3O4 + 2e−). H2 and CO2 gases were produced through the above catalytic reactions. The fraction of H2 gas in the outlet gas increased at a high heating temperature and was 30–50% at 700 °C. As a parallel reaction of the CO–H2O reaction, the supplied CO gas was decomposed to CO2 and solid carbon over Fe3O4 in the anode at low temperatures (disproportion of CO, 2CO → CO2 + C).