Recent Progress in Anode Materials for Solid Oxide Fuel Cells

In this paper, we report our recent progress in the development of anode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). Mo-doped Ce1-xMoxO2+delta (x = 0.05, 0.07, 0.1, 0.13) (CMO), Mo + RE-co-doped Ce0.9-xRExMo0.1O2.1-0.5x (x = 0.2, 0.3) (RE = Y, Sm, Gd) (CRMO) and Nd2WO6-type Sm(2-x)A(x)M(1-y)B(y)O(6-delta) (A = Ca, Sr; M = Mo, W; B = Ce, Ni) have been investigated in our laboratory. For CMO and CRMO, the formation of fluorite-like structure was confirmed by powder X-ray diffraction (PXRD) and the change in the lattice constant was found to be consistent with the Shannon ionic radius trend. CRMO samples treated under dry H-2 at elevated temperatures were found to retain the original fluorite structure while CMO showed presence of Mo in the PXRD. Sm(2-x)A(x)MoO(6-delta) (A = Ca, Sr) after heating under 97% H-2 +3% H2O up to 850 degrees C changed from Nd2WO6-type structure into Sm2MoO5 due to the reduction of Mo-VI that was confirmed by PXRD. For CRMO and SMO, the electrical conductivity was determined using 2-probe AC and DC methods and 4-probe DC method in wet H-2. The total electrical conductivity obtained from these two different techniques was found to be very close within the experimental error over the investigated temperature range. Among the CRMO samples studied, Ce0.75Sm0.2Mo0.1O2 exhibits the highest total conductivity of 7.8 x 10(-2) Scm(-1) at 450 degrees C in wet H-2 which is comparable to that of perovskite-type La0.75Sr0.25Cr0.5Mn0.5O3-delta. Nd2WO6-type Sm1.9Ca0.1MoO6-delta exhibits appreciable conductivity of 8.2 x 10(-2) Scm(-1) at 550 degrees C in wet H-2 with activation energy of 0.08 eV and it appears to be chemically stable against the reaction with YSZ electrolyte at 800 degrees C for 24 h in 97% H-2 +3% H2O.