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(C) Direct Methanol Fuel Cells (DMFCs)

         Laixia Yang and W. C. Huang, “Local Vapor Fuel Cell,” US Pat Pending (10/762,626) 01/23//2004.

2.                  Jiusheng Guo, A. Zhamu, and B. Z. Jang, “Organic Vapor Fuel Cell,” US Pat. Pending 11/257,528 (10/26/2005).

The direct methanol fuel cell (DMFC) is often considered the ideal energy source for portable devices and light-duty vehicle applications since (a) the power system is simpler, (b) a bulky and expensive catalytic reformer is not required, and (c) the liquid fuel, a methanol-water mixture, can potentially be distributed through the current petroleum distribution network. However, commercialization of the DMFC has been severely impeded by technological issues such as system complexity (including a problem with heat and water management), fuel cell stack bulkiness, a poor performance of electrodes (including high catalyst loading and methanol crossover), and high cost.

            These technological barrier issues have been addressed in the earlier studies conducted at Nanotek, which have demonstrated that a local heat source could help vaporize the liquid fuel diffused to the catalyst area, while allowing the remaining fuel in the anode to stay in a liquid state.  Specifically, in a local vapor fuel cell (LVFC), the fuel is fed in liquid form driven by capillary pressure, making it possible to have a compact, light-weight, and simple fuel cell configuration. This simple liquid-fed approach eliminates the need to have an external fuel vaporizer and blower. The anode catalyst, by design, operates on locally vaporized fuel (as opposed to liquid) and, as a result, exhibits a high electro-catalytic efficiency, leaving behind very little fuel that can potentially crossover the electrolyte layer. The resulting fuel cell exhibits dramatically improved fuel conversion efficiency, significantly reduced methanol crossover, and an impressive voltage-current curve featuring a higher voltage and a stable voltage output over a much wider current range (much higher power output). The high fuel efficiency is achieved by making the anode catalyst operate on fuel vapors at a higher local temperature. The fuel reactions in a vaporous state (at a higher temperature) could significantly reduce the needed amount of catalysts, making it possible to use lower-cost catalysts than Pt or Pt-Ru. The integrated system design permits good manufacturability and low cost.