Electrochemical reforming of CH4-CO2 mixed gas using porous yttria-stabilized zirconia cell

Flow rate and compositions of outlet gas and carbon deposition in the cell were studied upon the electrochemical reforming of 50% CH4-50% CO2 mixed gas using a cell of Ru-yttria-stabilized zirconia (YSZ) anode/porous 8 mol %-YSZ electrolyte/Ni-YSZ cathode system at 400-800 degrees C under 1.0 V/cm of electric field strength. The supplied mixed gas of 95-97% changed to H-2 and CO fuels at 800 degrees C (CH4 + CO2 -> 2H(2) + 2CO). As a parallel reaction, pyrolysis of CH4 occurred over a Ni cathode to produce carbon powder in the cell (CH4 -> C + 2H(2)), which decreased the flow rate of outlet gas at a high temperature. The above results were compared with the previously measured results with a porous Gd-doped ceria cell (mixed conductor of O2- ions and electrons). In the GDC cell, a part of deposited carbon was removed as CO gas by the reaction with O2- ions formed from CO2 gas in the cathode (CO2 + 2e(-) -> CO + O2-, C + O2- -> CO + 2e-) and the electrons produced were transported to the anode through the mixed conductor electrolyte film. (C) 2011 The Ceramic Society of Japan. All rights reserved.