Diffusion-limited electrochemical oxidation of H2/CO on Ni-anode catalyst in a CH4/CO2-solid oxide fuel cell

CH4/CO2-solid oxide fuel cell (SOFC) and CH4-SOFC have been studied at 750, 800, and 850 degrees C using a Ni anode, which is comprised of a porous Ni/ScSZ (Scandium-Stabilized Zirconia) catalyst interlayer and a porous Ni/YSZ (Yttrium-Stabilized Zirconia) anode support. CH4/CO2-SOFC denotes direct feeding CH4/CO2 to the anode chamber; and CH4-SOFC denotes direct feeding CH4. At open circuit, CH4/CO2-SOFC gave a lower anode activation loss (i.e., polarization) than CH4-SOFC. Analysis of product profiles revealed that CH4- and CH4/CO2-SOFC produced electricity from different reaction pathways. The performance of an anode-supported CH4/CO2-SOFC was diffusion-limited at temperatures above 800 degrees C. H-2/CO produced from CH4 dry reforming on the Ni/YSZ support became limiting reactants for electrochemical oxidation on the Ni/ScSZ catalyst interlayer. Electrochemical oxidation of CO is more diffusion-limited than that of H-2 because of its molecular size. Published by Elsevier B.V.