Low-temperature ceria-electrolyte solid oxide fuel cells for efficient methanol oxidation

Low temperature anode-supported solid oxide fuel cells with thin films of samarium-doped ceria (SDC) as electrolytes, graded porous Ni-SDC anodes and composite La(0.6)Sr(0.4)Co(0.2)Fe(0.8)O(3) (LSCF)-SDC cathodes are fabricated and tested with both hydrogen and methanol fuels. Power densities achieved with hydrogen are between 0.56 W cm(-2) at 500 degrees C and 1.09 W cm(-2) at 600 degrees C, and with methanol between 0.26 W cm(-2) at 500 degrees C and 0.82 W cm(-2) at 600 degrees C. The difference in the cell performance can be attributed to variation in the interfacial polarization resistance due to different fuel oxidation kinetics, e.g., 0.21 Omega cm(2) for methanol versus 0.10 Omega cm(2) for hydrogen at 600 degrees C. Further analysis suggests that the leakage current densities as high as 0.80 A cm(-2) at 600 degrees C and 0.11 A cm(-2) at 500 degrees C, resulting from the mixed electronic and ionic conductivity in the SDC electrolyte and thus reducing the fuel efficiency, can nonetheless help remove any carbon deposit and thereby ensure stable and coking-free operation of low temperature SOFCs in methanol fuels. (C) 2011 Elsevier B.V. All rights reserved.