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

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 degrees-800 degrees C under 1.25 V/cm of electric field strength. Use of Ni as anode accelerated the decomposition of CH4 (CH4 -> C + 2H(2)) 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 O2- ions (CO2 + 2e(-) -> CO + O2-). Use of Ru in both electrodes gave little problems to oxidize CH4 in anode (CH4 + O2- -> CO + 2H(2) + 2e(-)) and to reduce CO2 in cathode. SrRuO3 in anode worked also to oxidize CH4. This oxide reacted with H-2 produced in the reforming of CH4 to form Ru and Sr. Sr evaporated at 800 degrees C during the reforming. Stable formation of a H-2-CO fuel was measured for 11-13 h at 800 degrees C using the cells with Ni or Ru cathode and Ru anode. (C) 2009 The Ceramic Society of Japan. All rights reserved.