磺酸化polyhedral oligosilsesquioxane與Nafion複合膜於直接甲醇燃料電池之應用

本研究利用epoxy cyclohexyl polyhedral oligosilsesquioxane (ecPOSS)在末端進行開環反應，再與1, 4-butane sultone產生磺酸化反應，將磺酸化POSS (sPOSS)與Nafion溶液混合，利用塗佈法製備sPOSS/Nafion膜材。sPOSS使用FTIR與NMR做鑑定，確認磺酸根官能基確實有接枝在POSS末端，並且利用離子交換容積法與元素分析法，定量sPOSS內的磺酸根量，並且對複合膜材之鑑定包括熱穩定性、結晶度、含水吸附量、bound water比例、質子傳導性、3 M甲醇溶液吸附量、甲醇滲透性與單電池等性質分析且觀察其相互關係，以驗證膜材於燃料電池應用之可行性。在90 °C相對溼度為95 %操作條件下，可測得2 %與10 % sPOSS/Nafion膜材之質子傳導度比cast Nafion好，且10 % 複合膜材質子傳導度為6.7×10-2 S/cm大於Naion-117 (5.7×10-2 S/cm)，主要原因為bound water比例之提升；在70 °C操作溫度下，添加不同含量 sPOSS/Nafion複合膜材甲醇滲透係數皆小於cast Nafion與Naion-117，添加sPOSS量較少時，甲醇所需通過之路徑較曲折，且複合膜之結晶度較高，因此5 % sPOSS/Nafion複合膜材有最小之甲醇滲透係數，由單電池效能測試結果2 % sPOSS/Nafion膜材具有最高之電流密度與功率密度，其值分別為532 mA/cm2與36 mW/cm2比相同製程之cast Nafion好(394 mA/cm2 and 32 mW/cm2)，可綜合實驗結果得到2 % sPOSS/Nafion複合膜材質子傳導度比cast Nafion好，在甲醇滲透性質亦比cast Nafion低，因此2 % sPOSS/Nafion複合膜材具有最好之電池效能。

關鍵字

polyhedral oilgosilsesquioxane、有機無機複合膜、質子傳導度、甲醇滲透係數、直接甲醇燃料電池

並列摘要

Organic sulfonic acid groups were grafted onto epoxy cyclohexyl polyhedral oligosilsesquioxane (ecPOSS) through a ring opening reaction and the sulfonation reaction with 1, 4-butane sultone to form sulfonated polyhedral oligosilsesquioxane (sPOSS). The chemical structure of the sPOSS was confirmed by FTIR and NMR, and the degree of sulfonation was identified as 0.05 by sulfur content and ion exchange capacity. The composite membranes were cast from solutions of sPOSS and Nafion mixtures. The membranes were evaluated in terms of thermal stability, crystallinity, water uptake, bound water ratio, aqueous methanol (3 M) solution uptake, proton conductivity, methanol permeability, and single cell performance. The composite membrane contained 10 % sPOSS exhibited the highest proton conductivity of 6.7×10-2 S/cm at 90 °C and 95 % relative humidity. This value was higher than 5.7×10-2 S/cm of the Nafion-117 membrane measured in the same conditions. Composite membranes with various sPOSS content showed lower methanol permeability than the cast Nafion membrane. Finally, 2 % sPOSS/Nafion membrane showed the highest current density (532 mA/cm2) and power density (36 mW/cm2) among all the membranes tested with 3 M methanol in feed and at 70 oC.

並列關鍵字

Polyhedral oligosilsesquioxane, organic/inorganic composite membrane, proton conductivity, methanol permeability, direct methanol fuel cell

參考文獻

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磺酸化polyhedral oligosilsesquioxane與Nafion複合膜於直接甲醇燃料電池之應用

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