An Examination of Lanthanide Additives on the Performance of Cu-YSZ Cermet Anodes

The effect of various lanthanide additives on the performance of Cu-YSZ (yttria-stabilized zirconia), cermet anodes for solid-oxide fuel cells (SOFCs) was investigated at 973 K for H2 and the direct oxidation of butane. In all cases, the lanthanide oxides were added to the SOFC by impregnation of a porous YSZ matrix with aqueous solutions of the nitrate salts, followed by decomposition of nitrate ions by calcination. Ceria was found to be significantly more effective in promoting SOFC performance compared to the other lanthanides, and the performance of the lanthanide additives followed the catalytic activity observed for butane oxidation with 100 torr each of butane and O2. Samaria doping of ceria led to a slight decrease in performance but also decreased the catalytic active of ceria for butane oxidation. Membrane-reactor studies with propylene fed to Cu-molybdena-YSZ anodes at 723 K showed a high selectivity to acrolein, although Cu-ceria-YSZ anodes showed only total oxidation products under these conditions, implying that the catalytic properties of the oxides must be important. Finally, the application of these results to improved SOFC for direct oxidation of hydrocarbons is discussed.