Preparation of Freeze Cast T-SOFCs and a Universal Electrochemical Testing Fixture

Abstract

Direct Internal Reforming (DIR) has potential to increase the value proposition of Solid Oxide Fuel Cells (SOFCs) by improving the electrical conversion efficiency, simplifying the SOFC system, and reducing manufacturing costs. Utilizing DIR in SOFCs, however, presents technical challenges. These challenges include balancing the thermal-mechanical stress present along a dynamic fuel pathway; avoiding carbon build-up on the anode surface; anchoring the reforming catalysts to the anode without reducing electrochemical active area; and maintaining efficient and selective reformation of the hydrocarbon fuels. Deactivation of catalysts typically starts with build-up of excessive carbon that cascades into more severe problems that damage the cell and eventually lead to system failure. We believe the solution for achieving stable and efficient DIR in the SOFC requires an optimized anode microstructure that is tuned specifically for DIR. Conventional ceramic manufacturing processes for SOFCs are limited with regards to microstructural optimization such as providing a hierarchical fuel pathway while maintaining high surface area. In this research, we have characterized and optimized a manufacturing process referred to as freeze casting of tubular SOFCs (T-SOFCs). The freeze casted anode was modified as a function of processing conditions and then was examined with techniques such as B.E.T. surface area measurements, scanning electron microscopy, and X-ray diffraction. The processing conditions that were optimized included changes in the slip formulation, casting temperatures, and freeze drying conditions. Electrochemical evaluation of the tubular SOFCs made via the freeze cast process revealed state-of-art performance and while creating an optimized surface for anchoring DIR catalysts. A universal electrochemical performance testing fixture for T-SOFCs is also discussed.