Methane Electrochemical Oxidation Pathway over a Ni/YSZ and La0.3Sr0.7TiO3 Bi-Layer SOFC Anode

The electrochemical conversion of dry CH4 was studied over a Ni/YSZ and La0.3Sr0.7TiO3 bi-layer anode at 1023 K. In order to understand the electrochemical pathway, a fuel mixture composed of H-2, CH4, CO, and CO2 was fed to the SOFC anode while the gas products were analyzed at different current densities. In this fuel mixture, the Nernst potential and material balance, calculated from the H-2 electrochemical oxidation reaction, were consistent with the experimental OCV and the gas product analysis. In dry CH4 fuel, the electrochemical oxidation pathway is more complex. The conversion of dry CH4 strongly depends on the anode polarization. CO formed at low current densities (i < 0.1 A/cm(2)) from the electrochemical oxidation of carbon deposits, whereas H2O and CO2 formed above this current density from the electrochemical oxidation of H-2 and CO. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.001204jes] All rights reserved.