Description:
OBJECTIVE: Develop new biomimetic membranes with chemical stability and reduced methanol crossover to enable micro direct methanol fuel cells (DMFCs). DESCRIPTION: The Army has need for high-energy density, lightweight power sources for the dismounted warrior. Currently methanol fueled polymer electrolyte based fuel cells suffer from methanol cross over which reduces overall system efficiency and necessitates the use of diluted methanol solutions decreasing the system specific energy. Biomimetic membranes with ion channels either inspired by natural systems or membranes with channels from organisms offer several potential advantages including improved conductivity and selective permeability. At the same time bioderived systems represent several challenges including: chemical stability, dehydration, the ability to integrate bioderived materials into synthetic membranes, and the challenges of orienting and aligning pores to allow their use in thicker mechanically robust membranes. PHASE I: In phase I biomimetic membranes will be produced and evaluated to demonstrate feasibility for use in fuel cells. Specific goals should include the ability to prepare mechanically robust membranes that have conductivities on par with their Nafion based counterparts, reduced methanol crossover, chemical stability when exposed to high methanol concentrations which can both denature and dehydrate the biomimetic pores, and evaluate the membrane in a direct methanol half cell. Preliminary results should support the potential to develop a robust 1W system which can utilize 15M or higher methanol solutions with reduced methanol crossover. PHASE II: In phase II, based on the results from the successful phase I program, design, construct, and evaluate a DMFC 1W passive fuel cell with a stack based on biomimetic membranes. The system must have a lifetime exceeding 500 hours, a system energy density exceeding 1500 Wh/kg, and be able to directly utilize concentrated methanol (>15M). Two systems will be delivered to the US Army for testing and evaluation. PHASE III: Biomimetic membranes will be integrated into larger power fuel cell stacks for both military and civilian power applications. These systems will have higher efficiencies and lighter system weights than the current state of the art systems. Bothe the military and civilian sectors are seeking compact light weight power sources for dismounted soldiers and civilian electronic devices. The biomimetic membranes for DMFCs have the potential to transition to both soldier borne and solider transportable applications to either power devices directly on the soldier or to serve as a power source to recharge secondary batteries. Likely sources of funding if the phase III program is successful include PEO Soldier and CERDEC. REFERENCES: 1. Xie, C., J. Bostaph, and J. Pavio. 2004. Development of a 2 W direct methanol fuel cell power source. Journal of Power Sources 136:55-65. 2. Broussely, M., and G. Archdale. 2004. Li-ion batteries and portable power source prospects for the next 5-10 years. Journal of Power Sources 136:386-394. 3. Kim, D. J., E. A. Cho, S. A. Hong, I. H. Oh, and H. Y. Ha. 2004. Recent progress in passive direct methanol fuel cells at KIST. Journal of Power Sources 130:172-177. 4. Shimizu, T., T. Momma, M. Mohamedi, T. Osaka, and S. Sarangapani. 2004. Design and fabrication of pumpless small direct methanol fuel cells for portable applications. Journal of Power Sources 137:277-283. 5. Kim, H. 2006. Passive direct methanol fuel cells fed with methanol vapor. Journal of Power Sources 162:1232-1235. 6. Gupta, G., P. Atanassov, and G. P. Lopez. 2006. Robust hybrid thin films that incorporate lamellar phospholipid bilayer assemblies and transmembrane proteins. Biointerphases 1:6-10. 7. Montal, M., and P. Mueller. 1972. Formation of Bimolecular Membranes from Lipid Monolayers and a Study of Their Electrical Properties. Proceedings of the National Academy of Sciences of the United States of America 69:3561-3566. 8. Ly, H. V., and M. L. Longo. 2004. The influence of short-chain alcohols on interfacial tension, mechanical properties, area/molecule, and permeability of fluid lipid bilayers. Biophysical Journal 87:1013-1033. 9. Lee, W., H. Kim, T. K. Kim, and H. Chang. 2007. Nation based organic/inorganic composite membrane for air-breathing direct methanol fuel cells. Journal of Membrane Science 292:29-34. 10. Akeson, M., and D. W. Deamer. 1991. Proton Conductance by the Gramicidin Water Wire - Model for Proton Conductance in the F1F0 ATPases. Biophysical Journal 60:101-109.
