Novel Electrode Materials for Low-Temperature Solid Oxide Fuel Cells

Abstract

Fuel cell performance depends strongly on the anode microstructure, which is determined by the anode compositions and fabrication conditions. Four types of anodes with two kinds of NiO and GDC powders were investigated. By carefully adjusting the anode microstructure, the GDC electrolyte/anode interfacial polarization resistances reduced dramatically. The interfacial resistance at 600 C decreased from 1.61 {Omega} cm{sup 2} for the anodes prepared using commercially available powders to 0.06 {Omega} cm{sup 2} for those prepared using powders derived from a glycine-nitrate process. The critical issues facing the development of economically competitive SOFC systems include lowering the operation temperature and creating novel anode materials and microstructures capable of efficiently utilizing hydrocarbon fuels. Anode-supported SOFCs with an electrolyte of 20 {micro}m- thick Gd-doped ceria (GDC) were fabricated by co-pressing, and both Ni- and Cu-based anodes were prepared by a solution impregnation process. At 600 C, SOFCs fueled with humidified H{sub 2}, methane, and propane, reached peak power densities of 602, 519, and 433 mW/cm{sup 2}, respectively. Both microstructure and composition of the anodes, as fabricated using a solution impregnation technique, greatly influence fuel cell performance. Although steam reforming or partial oxidation is effective in avoiding carbon deposition of hydrocarbon fuels, it increases the operating cost and reduces the energy efficiency. A catalyst (1 %wt Pt dispersed on porous Gd-doped ceria) for pre-reforming of propane was developed with relatively low steam to carbon (S/C) ratio ({approx}0.5), coupled with direct utilization of the reformate in low-temperature SOFCs. Propane was converted to smaller molecules during pre-reforming, including H{sub 2}, CH{sub 4}, CO, and CO{sub 2}. A peak power density of 247 mW/cm{sup 2} was observed when pre-reformed propane was directly fed to an SOFC operated at 600 C. No carbon deposition was observed in the fuel cell for a continuous operation of 10 hours at 600 C.