Development of electrochemical cell with layered composite of the Gd-doped ceria/electronic conductor system for generation of H2–CO fuel through oxidation–reduction of CH4–CO2 mixed gases

This paper shows the recent results on the development of layered composite promoting two types of electrochemical reactions (oxidation and reduction) in one cell. This cell consisted of porous Ni–Gd-doped (GDC) ceria cathode/thin porous GDC electrolyte (50 μm)/porous SrRuO3–GDC anode. The external electric current was flowed in this cell at the electric field strength of 1.25 and 6.25 V/cm. The mixed gases of CH4 (30–70%) and CO2 (70–30%) were fed at the rate of 50 ml/min to the cell heated at 400–800 °C under the electric field. In the cathode, CO2 was reduced to CO (CO2 + 2e− → CO + O2−) and the formed CO and O2− ions were transported to the anode through the pores and surface and interior of grains of GDC film. On the other hand, CH4 was oxidized in the anode to form CO and H2 through the reaction with diffusing O2− ions (CH4 + O2− → CO + 2H2 + 2e−). As a result, H2–CO mixed fuel was produced from the CH4–CO2 mixed gases (CH4 + CO2 → 2H2 + 2CO). This electrochemical reaction proceeded completely at 800 °C and no blockage of gases was measured for long time (>10 h). Only H2–CO fuel was generated in the wide gas compositions of starting CH4–CO2 gases.