甲醇穿透對直接甲醇燃料電池性能影響之研究

The Effect of membrane thickness, cell temperature, and methanol concentration on methanol crossover and fuel cell performance

杜承鑫(Cheng Hsin Tu)

指導教授 ： 蘇艾

元智大學/工程學院/機械工程學系/碩士(2003年)

摘要

摘 要
直接甲醇燃料電池中甲醇穿透會影響發電效率，雖然甲醇會與陰極端的氧氣氧化，但穿透的甲醇會造成過電位，降低燃料的利用率，影響發電效率。本研究以DMFC為研究對象，改變操作條件(電解質厚度、電池溫度、甲醇溶液濃度及自製MEA)，分析這些參數對DMFC甲醇穿透及效能之影響。固定薄膜厚度下，溫度增加會明顯提昇性能，低濃度之甲醇導致濃度極化提前發生降低電池性能；高濃度之甲醇雖能延遲濃度極化，高溫操作會造成甲醇穿透更趨嚴重而降低電池性能。甲醇穿透嚴重性可由開路電壓觀察得之，開路電壓值與甲醇穿透量成反比，研究發現開路電壓與電解質厚度及操作溫度成正比，與甲醇濃度成反比。雖電解質厚度增加雖能降低甲醇穿透，但電解質厚度的增加同時增加離子的傳遞距離和歐姆阻抗，使Nafion 117 (180μm)所組成的電池性能明顯低於Nafion 112(50μm)的電池。 關鍵字:直接甲醇燃料電池、過電位、甲醇穿透、濃度極化

關鍵字

直接甲醇燃料電池 ； 甲醇穿透 ； 過電位 ； 濃度極化

並列摘要

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

並列關鍵字

direct methanol fuel cell (DMFC) ； Crossover ； Overpotential ； concentration polarization

參考文獻

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