Operation of a Novel Dry Hydrocarbon Tolerant Intermediate Temperature Solid Oxide Fuel Cell

Many factors including lower materials cost for stack and balance of plant components drive an effort to reduce the operating temperature of SOFCs. Sr- and Mg-doped LaGaO3 (LSGM) has gained popularity as an intermediate temperature electrolyte due to its high oxygen conductivity. However, challenges remain regarding its mechanical strength and the lack of suitable electrode materials due to incompatibilities with conventional anode and cathode materials. Additionally, operation of conventional solid oxide fuel cells on dry hydrocarbon gas streams is precluded by the catalyzed formation of carbon whiskers within the matrix of nickel-based anodes. The incompatibility of LSGM with conventional anodes allows for investigation of other benefits of a Ni free anode; among which are hydrocarbon tolerance and redox stability. LSGM electrolyte supported cells were fabricated to test the performance and hydrocarbon tolerance of a Ni-free materials set. The composite anode was comprised of Sr-, Mg- and Co-doped LaGaO3 (LSGMC), La-doped CeO2 (LDC) as a catalytic component and Y-doped SrTiO3 as a conductive component. The cathode was made from a composite of LSGMC and Sm-doped SrCoO3. Materials were synthesized by wet chemical methods, characterized and fabricated into durable cells of high quality. The processing conditions of anode conductive components are discussed as an important factor impacting the performance of the cells. The cells were tested in dry methane and hydrogen. Testing showed cell voltages very near theoretical voltage indicating that sealing and electrolyte quality were excellent. Temperature cycling performance and post-test inspection showed that durability of the materials set was achieved. The cell showed a low power density when operating on hydrocarbons directly. Cells had no visible degradation in performance or coking after operation on dry hydrocarbons, in stark contrast to nickel-based anode performance under the same operating conditions. Poor catalytic activity to the reforming process and direct reaction of methane were found to contribute to the overall low performance. Strategies for improving catalytic activity without introducing coke-promoting materials are discussed.