Electrochemical reforming of CH₄-CO₂ gas using porous Gd-doped ceria electrolyte with Ni and Ru electrodes

Abstract

Electrochemical reforming of 50% CH₄-50% CO₂ mixed gas was investigated using the cell of Ni or Ru-GDC (Gd-doped ceria) cathode/porous GDC electrolyte/Ni, Ru or SrRuO₃-GDC anode system at 400°-800°C under 1.25 V/cm of electric field strength. Use of Ni as anode accelerated the decomposition of CH₄ (CH₄ → C + 2H₂) and caused the blockage of supplied gas because of the deposition of carbon in the open spaces of anode. On the other hand, Ni in cathode worked well to reduce CO₂ to CO and O^2- ions (CO₂ + 2e^- → CO + O^2-). Use of Ru in both electrodes gave little problems to oxidize CH₄ in anode (CH₄ + O^2- → CO + 2H₂ + 2e^-) and to reduce CO₂ in cathode. SrRuO₃ in anode worked also to oxidize CH₄. This oxide reacted with H₂ produced in the reforming of CH₄ to form Ru and Sr. Sr evaporated at 800°C during the reforming. Stable formation of a H₂-CO fuel was measured for 11-13 h at 800°C using the cells with Ni or Ru cathode and Ru anode.