Methane On-Cell Reforming by Alloys Reduced from Ni0.5Cu0.5Fe2O4 for Direct-Hydrocarbon Solid Oxide Fuel Cells

Ni0.5Cu0.5Fe2O4 (NCFO)-Gd0.1Ce0.9O1.95-d (GDC) composite was imposed on NiO-Y2O3 stabilized ZrO2 (YSZ) anode by screen-printing and sintering, and reduced in situ to form a layer of metal (Ni-Fe and Ni-Cu alloys, NCF)-GDC cermet on Ni-YSZ, functioning as a catalyst for CH4 on-cell reforming. The double-layer anode NCF-GDC/Ni-YSZ (DA) was investigated by electrochemical impedance spectroscopy and direct current polarization in H2-3 mol% H2O and CH4-x mol% H2O (x = 3 [?] 20) at various temperatures between 650 and 800degC. For comparison single-layer Ni-YSZ anode (SA) was also evaluated. The polarization resistance of the DA decreased to 1/3 and 1/2 of that of the SA in H2-3 mol% H2O and CH4-3 mol% H2O, respectively, due to the increase in anode thickness and carbon deposition resistance. This improvement was also supported by the results of direct current polarization, SEM examination and Ramann spectroscopy. Carbon deposition was avoided in the DA during the test at 800degC and 200 mA cm[?]2 for 24 h by slightly increasing the H2O content to the level of 7 mol% in the CH4-H2O mixture. Excessive amount of H2O (20 mol% H2O) was found to deteriorate the electrochemical performance of the DA by fuel dilution.