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). Gd-doped ceria (GDC) particles with composition of Gd 0.1 Ce 0.9 O 2 were suspended in ethanol containing nitrates of Sm, Sr, and Co in a molar ratio of 1:1:2 to form Sm 0.5 Sr 0.5 CoO 3 (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 Ωcm 2 at 450 °C to 0.45 Ωcm 2 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/cm 2 were achieved at 500 and 600 °C, respectively.