Description:
OBJECTIVE: Exploration of alternative approaches to generate hydrogen from methanol without thermal reforming. Current thermal reformers operate at elevated temperatures. Novel methanol electrolysis processes that converts methanol into hydrogen for use in low power fuel cells will be developed. DESCRIPTION: Current low power Army Fuel cells that are being developed either steam reform methanol to generate hydrogen for subsequent use in a fuel cell or directly convert the methanol into electrical power in direct methanol fuel cells. Thermal reforming increases system complexity and thermal signature while DMFC require large over potentials for methanol oxidization. In addition methanol has the tendency to transport through polymer electrolyte membranes (PEM) with three negative consequences: 1. Methanol at the cathode acts to depolarize the cathode, further reducing the cell potential, and with it the electrical energy yield. 2. Methanol that is not oxidized at the anode does not contribute to the current delivered by the fuel cell. 3. Methanol that is consumed at the cathode yields additional water and carbon dioxide increasing the air flow required for operation. In addition, in current DMFCs trace amounts of ruthenium from the anode diffuses through the membrane and gradually poison the cathode for oxygen reduction. Methanol electrolysis offers a potential a low temperature approach to generate hydrogen efficiently from methanol to circumvent the inefficiencies associated with methanol crossover /ruthenium poisoning and the system complexity and thermal signature of traditional steam reforming. Because the potential required to convert methanol to hydrogen is less than the over potential to oxidize it in a fuel cell, electrolytic reforming has the potential to realize enhanced energy yield due to an increase in overall system potential. In addition, while a conventional DMFC typically operates on dilute methanol, 3 molar or less, with an electrolyzer included in the system methanol can be supplied as an equimolar mixture of methanol and water. PHASE I: Methanol electrolysis will be demonstrated using advanced electrocatalysts and the products characterized. Efficiency will be characterized to show improved performance over state of the art direct methanol fuel cells. Concepts to integrate the electrolyzer into a fuel cell system will be developed. PHASE II: In phase II, based on the results from the successful phase I program, two 25W methanol electrolysis fuel cell systems with performance exceeding current state of the art direct methanol fuel cell systems will be developed and delivered to the US Army for testing and evaluation. PHASE III DUAL USE APPLICATIONS: Advanced methanol electrolysis hydrogen generation technology for fuel cells will significantly impact both military and commercial applications, accelerating product development, particularly for lightweight low power devices. Because the market and the number of devices in the commercial sector is much larger than the military market, widespread usage of this technology will drive down the cost of devices for the military and ensure a reliable manufacturing base. The methanol electrolysis technology will transition into fuel cell system technology for dismounted soldiers. Likely sources of funding if the phase III program is successful include PEO Soldier and CERDEC. Applications for the advanced methanol fuel cell systems include soldier power to complement batteries and to charge lithium-ion rechargeable batteries, significantly reducing the logistical burden (weight and volume) for the soldier by reducing the number of batteries required for extended mission time as well as a many civilian electronics applications. REFERENCES: 1. Z. Hu, M. Wu, Z. Wei, S. Song, and P. K. Shen, J. Pow.., 166, 458-461 (2007). 2. G. Sasikumar, A, Muthumeenal, S. Pethaiah, N. Nachiappan, and R. Balaji, Int. J. Hyd. Energ., 33, 5905 5910 (2008). 3. R. F. de Souza, G. Loget, J. C. Padilha, E. M. A. Martini and M. O. De Souza, Electrochem. Comm., 10, 1673 1675 (2008). 4. T. Maiyalagan, Int. J. Hyd. Energy., 34, 2874 2879 (2009). 5. T. Take, K. Tsurutani, and M. Umeda, J. Pow. Sourc., 164, 9 16 (2007). 6. Barbara Jeffries-Nakamura, Sekharipuram R Narayanan, Thomas I Valdez, William Chun, NASA TECH BRIEF Vol. 26, No. 6 from JPL NEW TECHNOLOGY REPORT NPO- 19948 (2002).
