| Summary: | 碩士 === 元智大學 === 機械工程學系 === 91 === ABSTRACT
Methanol crossover will largely affect the efficiency of power generation in direct methanol fuel cell. Although methanol will spontaneously oxidize at the cathode, it also causes serious overpotential and conversion loss in terms of lost fuel. In this study, by changing the operating condition (ex. membrane thickness, cell temperature, methanol solution concentration), we found how these parameters affect methanol crossover and power generation in direct methanol fuel cell. By fixing the membrane thickness, we found that the increasing temperature will obviously promoting the cell performance, and low methanol solution concentration will cause concentration polarization therefore resulting in lower cell performance. Although high methanol solution concentration will overcome the concentration polarization, serious methanol crossover will lower the cell performance at high operating temperature. From this study, we found that open circuit voltage will be in inverse proportion to methanol solution concentration and methanol crossover, and will be in proportion to membrane thickness and cell temperature. Although increasing membrane thickness will lower the degree of methanol crossover, it will also increases the distance for ion to transport. Therefore, the cell performance including Nafion 117 is lower than Nafion 112.
Keywords: direct methanol fuel cell (DMFC)，Overpotential，Crossover，concentration polarization
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