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

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).