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_0.6Sr_0.4Co_0.2Fe_0.8O₃ (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 °C and 1.09 W cm⁻² at 600 °C, and with methanol between 0.26 W cm⁻² at 500 °C and 0.82 W cm⁻² at 600 °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 Ω cm² for methanol versus 0.10 Ω cm² for hydrogen at 600 °C. Further analysis suggests that the leakage current densities as high as 0.80 A cm⁻² at 600 °C and 0.11 A cm⁻² at 500 °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.