| Summary: | 碩士 === 元智大學 === 機械工程學系 === 98 === A significant advantage of direct methanol fuel cells (DMFCs) is the high specific energy of the liquid fuel. Nevertheless, conventional DMFCs have to be operated with excessively diluted methanol solutions to limit methanol crossover. Methanol crossover not only causes a mixed potential on the cathode, decreasing the cathode potential, but also leads to a waste of fuel which lowers the overall efficiency of the cell. This article experiments on the design of anode gas diffusion layer to confer the relationships between its physical characteristic and MEA performance.
The GDL P5M20-2 operates on 2M methanol has immediate performance with commercial GDL SGL 34BC. With the increasing of methanol concentration, the performance of P5M20-2 always couldn’t surpass the commercial one. Base on the P5M20-2 that extended the Graded Micro Porous Layer (GMPL), which has lower performance while operate on low methanol concentration. With the increase of methanol concentration, the decay of performance is not obvious as single layer MPL. It reveals that the hydrophobic gradient from GMPL has the effect on resist methanol crossover. The GMPL-3L, which has 5mg/cm2 carbon loading, even keep more than half of the performance on 2M methanol solution while operates on 8M methanol solution. It proves that GMPL with the hydrophobic gradient has the effect on resist methanol crossover and the more carbon loading has compensation for high concentration methanol solutions.
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