磺化聚苯乙烯混摻改質蒙托土於直接甲醇燃料電池質子交換膜之研究

直接甲醇燃料電池在電力供應上，較適用於小功率的行動式能源供應系統。現今此燃料電池仍有幾個技術尚未突破，主要為質子交換膜中的質子傳導率(Conductivity, C)和甲醇滲透率(Permeability, P)，以及觸媒的轉化之能力為最需要被改善的因素。在質子交換膜中目前全都以全氟化磺酸膜為主，如杜邦的Nafion®薄膜，但由於其甲醇滲透率過高，為不能將直接甲醇燃料電池商業化的最關鍵因素，故現今仍有許多研究者在尋找替代材料來製備價廉且有優秀表現的質子交換膜。本研究以polystyrene為主材料，以部分磺化的方式，使其具有質子交換膜之適用性。文獻指出部分磺化的聚苯乙烯在質子傳導率/甲醇滲透率的比值上有高於Nafion薄膜之表現，本研究探討使用其他溶劑成膜，與文獻比較在質子交換膜的表現。本研究進而加入蒙托土(Montmorillonite, MMT)為添加物，希望藉由其廣大的比表面積及不透水性來減少甲醇的滲透，以有機/無機複合材料之特性來提升高分子之物理及化學性質。研究以不同溶劑、磺化率及蒙托土的添加量來比較質子傳導率、甲醇滲透率等性質之改變，最後以質子傳導率/甲醇滲透率之比值(C/P)來評估此材料之表現。經由實驗結果指出，使用二甲基亞碸做部分磺化聚苯乙烯的成膜溶劑，會有最佳的效果，磺化率於14.38%之C/P值表現為Nafion 117之1.9倍。添加蒙托土後的部分磺化聚苯乙烯薄膜，其甲醇滲透率的降低並未如想像，但可以改善材料的熱穩定性，添加1%蒙托土有較佳的熱穩定性，最多可將熱裂解溫度提升15oC。蒙托土的分散若使用氯苯以及正丁醇為溶劑，可有最佳的蒙托土分散效果，由TEM及XRD的鑑定結果為脫層型分散。

關鍵字

直接甲醇燃料電池；質子交換膜；磺化聚苯乙烯蒙托土

並列摘要

Direct methanol fuel cell has potential for small power supply to portable devices. At the moment, there are still several serious barriers for DMFC application. First, the performance of conductivity and permeability of proton exchange membrane is not well enough. The other problem is the slow electrode kinetics of methanol in the present of electrocatalyst. Perfluoro-carbon sulfonic acid such as Nafion® membrane has been used for proton exchange membrane. But the methanol permeability of Nafion membrane is still high. In this study, polystyrene is prepared and used for direct methanol fuel cell. The ratio of proton conductivity to methanol permeability for partial sulfonated polystyrene is higher than Nafion. The performances of various membranes by using various solvents for membrane preparation has been investigated. Modified montmorillonite (MMT) of nano clay, which has large surface area were blended with partial sulfonated polystyrene, and were intended to be used for reducing methanol permeability. The performance of membrane using dimethyl sulfoxide as solvent is better than other solvents. The membrane with degree of sulfonation 14.38% has the C/P ratio 1.9 times of Nafion. We have found that MMT blended with partial sulfonated polystyrene couldn’t reduce methanol permeability as expected. The membrane thermal stability can be enhanced by blending MMT. Mixing 1 wt% MMT with sulfonated polystyrene can raise the decomposition temperature about 15 oC. Using chlorobenzene/n-butanol as solvent the dispersion of MMT in sulfonated polystyrene can be found to be exfoliated from TEM and XRD analyses.

並列關鍵字

DMFC ； Proton exchange membrane ； Sulfonation ； Polystyrene ； Montmorillonite

參考文獻

顏在德, “無機/高分子混成材料質子交換膜”, 碩士論文, 台灣大學 (2006).

衣寶廉, “燃料電池-原理與應用”, 五南圖書出版公司 (2005).

Bae, B., and Kim, D., “Sulfonated polystyrene grafted polypropylene composite electrolyte membranes for direct methanol fuel cells”, J. Membrane Science, 220, p75-87 (2003).

Bae, B., Heung Y. H., and Kim, D., “Nafion®-graft-polystyrene sulfonic acid membranes for direct methanol fuel cells”, J. Membrane Science, 276, p51 (2006).

Carretta, N., Tricoli, V., and Picchioni, F., “Ionomeric membranes based on partially sulfonated polystyrene: synthesis, proton conduction and methanol permeation”, J. Membrane Science, 166, p189 (2000).

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磺化聚苯乙烯混摻改質蒙托土於直接甲醇燃料電池質子交換膜之研究

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