Freeze Casting of Tubular Sulfer Tolerant Materials for Solid Oxide Fuel Cells

Solid oxide fuel cells have long suffered from degradation due to impurities in the fuel and complexities associated with dissimilar materials and high operating temperatures. This degradation lowers the usable cell power output and requires ancillary equipment for fuel sulfur removal and reformation. A unique microstructure for a tubular anode-supported SOFC is being developed using a novel freeze-casting technique, with the promise of increasing the cell triple phase boundary area and resulting in higher power density. An infiltration of the freeze-cast anode with a newly discovered mixed metal oxide catalyst is showing great promise in increasing the sulfur and coking tolerance of the anode. In the recently completed two-year Phase II effort, continued anode tube freeze-casting development of sub-scale and full-scale size tubes was completed, and then infiltrated with the novel catalyst material. Electrolyte and cathode coating processes were successfully demonstrated, and single-cell performance tests were performed using multiple sulfur-laden fuel gases.  Finally, a conceptual 250W man-portable design was developed and fabricated and used for preliminary testing.  This project is a collaboration between Millennitek, who has developed the tubular freeze-casting technology, Georgia Institute of Technology (Georgia Tech), who is developing the anode catalyst technology and is performing the electrochemical testing, and Special Power Sources (SPS), who is a manufacturer of tubular SOFC's.  In the Sequential Phase II project, SOFC bundle tests will be performed utilizing directly-injected sulfur-laden liquid fuels, to determine long-term performance.  Improvements to the 250W man-portable generator design will be completed, and tested for long-term performance in parallel to the laboratory performance testing.  A prototype generator will be delivered to the Army at the conclusion of this project.