Processing and Properties of Nanocomposite Thin Films for Micro-Solid Oxide Fuel Cell Applications

Microfabricated solid oxide fuel cells (micro-SOFCs) have recently gained attention as a promising technology, with the potential to offer a low temperature (as low as 300^oC), reduced start-up time, and improved energy density for portable power applications.  As a means for achieving the substantially reduced operating temperatures, new electrode materials with increased catalytic activity are being explored.  At present, porous Pt is the most common cathode being investigated for micro-SOFCs. However, there are significant technical challenges for utilizing pure metallic electrodes at the operating temperatures of interest due to their tendency towards Ostwald ripening, as well as low bulk ionic conductivity. Nanocomposite materials (e.g. Pt/YSZ) are being studied as a promising alternative approach for providing both microstructural and electrochemical stability to the electrode layer.  The microstructure and composition of the nanocomposite cathode material has been systematically investigated via controlled vacuum deposition conditions and resultant electrochemical properties measured by electrochemical impedance spectroscopy (EIS). Transmission electron microscopy (TEM) of the nanocomposite films reveals a percolating network of Pt and YSZ, along with interconnected nano-sized pores.  An improvement in charge transfer kinetics associated with the oxygen reduction reaction has been demonstrated as compared to a pure porous Pt electrode, along with a significant improvement in microstructural stability during extended mSOFC operation.  These results will be presented in detail.