Nanocomposite Electrodes Fabricated by a Particle-Solution Spraying Process for Low-Temperature SOFCs

We report a particle-solution spraying process for fabrication of porous electrodes for solid oxide fuel cells (SOFCs). Gddoped ceria (GDC) particles with composition of Gd0.1Ce0.9O2 were suspended in ethanol containing nitrates of Sm, Sr, and Co in a molar ratio of 1:1:2 to form Sm0.5Sr0.5CoO3 (SSC) after combustion in air. The SSC solution carrying GDC particles was pumped through an atomizer and the resulting mist was combusted, depositing a porous composite layer consisting of SSC and GDC on a GDC electrolyte supported by a Ni-GDC anode. Typically, the SSC-GDC composite cathodes consist of large GDC grains (1-2 µm) embedded in nanosized phases of SSC. The highly open porous structure significantly facilitates gas transport while the extremely large surface area dramatically enhances electrode kinetics. As a result, the polarization resistances to oxygen reduction of the GDC-SSC/GDC interface are extremely low, varying from 1.06 (omega)cm2 at 450 °C to 0.45 (omega)cm2 at 500 °C. The activation energy for the electrode reaction was estimated to be about 0.65 eV (62.5 kJ/mol), as determined from impedance spectroscopy performed at different temperatures. For a single cell with a configuration of SSC-GDC/GDC/Ni-GDC, peak power densities of 223 and 385 mW/cm2 were achieved at 500 and 600 ° C, respectively.