Development of new fabrication methods for solid oxide fuel cell electrodes

Solid oxide fuel cells (SOFC) have gained a great deal of attention in recent years since they have the potential to be high efficiency devices for the generation of electricity. The ability to use hydrocarbon fuels however requires the development of alternatives to conventional Ni/YSZ anodes that are prone to coking when exposed to hydrocarbons. The optimization of electrode microstructure and composition is also needed in order to maximize the electrode catalytic activity and thermal stability. In this thesis these issues were addressed through the development of new methods for anode fabrication that allowed for the incorporation of a wide range of materials and better control of electrode microstructure. The specific methods that were studied include (1) Impregnation with urea and (2) Electrochemical Deposition. First, how impregnation using Cu(NO3)2 and urea affect the microstructure of the Cu component in Cu/CeO2/YSZ (yittria-stabilized zirconia) composite anodes and how this influences anode performance were examined. This method produced a more homogeneous distribution of Cu throughout the anode than impregnation with only Cu(NO3)2. Second, Cu electrodeposition into 0.12 cm thick, highly porous Ni/YSZ cermets was investigated for the initial study to evaluate electrodeposition for the electrode fabrication method. An electrochemical cell in which the electrolyte solution was allowed to flow through the porous Ni/YSZ substrate was constructed in order to eliminate mass transfer limitations and determine conditions for which the potential drop in the electrolyte solution was minimized for the deposition of uniform Cu layer in the cermet. Finally it was demonstrated how the anodes for SOFCs could be prepared by electrodeposition. After the addition of CeO2, a 60 μm thin porous layer of YSZ was made conductive by the deposition of a conductive carbon layer with exposing the porous layer to C4H10 at 1123 K and either Ni or Co was then electrodeposited on the conductive porous layer to produce the metal-ceramic composite anode. High metal loadings in the porous anode could be obtained. In addition a cell with a Cu-Co bimetallic anode was also prepared by electrodeposition of Cu onto the Co