- 學位論文
磺酸化Polyhedral Oligosilsesquioxane與磺酸化Poly(phthalazionone ether ketone) 複合膜於直接甲醇燃料電池之應用
Sulfonated Polyhedral Oligosilsesquioxane/ Sulfonated Poly(phthalazionone ether ketone) Composite Membranes for Application in Direct Methanol Fuel Cells
摘要
本研究利用sulfonated polyhedral oligosilsesquioxane (sPOSS) 與sulfonated poly(phthalazionone rtherketone) (sPPEK) 摻混，製備有機/無機聚電解質膜材，探討應用於甲醇燃料電池上之性質。於無機材料epoxy cyclohexyl polyhedral oligosilsesquioxane (ecPOSS)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sPPEK溶液混合，利用塗佈法製備複合膜材。sPOSS使用FTIR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、溶液吸附量、bound water ratio、質子傳導性、甲醇滲透性與單電池測試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。 磺酸化PPEK隨著磺酸化程度提高，在高溫操作環境下其分子結構變得較為鬆散，水分子容易進入膜材內而造成嚴重的彭潤性，在水含量測試中，80 °C時未改質的sPPEK膜材產生嚴重膨潤，而添加sPOSS的複合膜材依然維持良好的尺寸穩定性，造成這個現象可能的原因為sPPEK與sPOSS分子上官能基彼此之間產生特殊之作用力(由-SO3H與-OH酸鹼型作用力或-SO3H與-SO3H鍵結)，使得分子鏈比較不容易移動，由結果證明添加sPOSS可使sPPEK膜材在高溫操作下可維持膜材的穩定性並改善與觸媒層貼合的程度。膜材質子傳導度方面，在90 °C相對溼度為95 %操作條件下，可測得sPOSS/sPPEK膜材之質子傳導度比未改質的sPPEK膜材來的高，且含5 % sPOSS複合膜材質子傳導度可達2.6×10-2 S/cm，主要原因可能為sPOSS上的磺酸根吸附水分子，有助於形成質子傳遞的通道；在70 °C操作溫度下，添加不同含量 sPOSS/sPPEK複合膜材甲醇滲透係數皆小於cast Nafion與Naion-117，當添加少量sPOSS在膜材內形成立體障礙，甲醇所需通過之路徑較曲折，因此5 % sPOSS/sPPEK複合膜材有最小之甲醇滲透係數。由單電池效能測試結果5 % sPOSS/sPPEK膜材具有最高之電流密度與功率密度，其值分別為253 mA/cm2與32 mW/cm2，結果比相同製程之純sPPEK膜(189 mA/cm2 and 18 mW/cm2)為優， 5 % sPOSS/sPPEK複合膜材之質子傳導度比sPPEK好，甲醇滲透係數亦比sPPEK低，因此導致5 % sPOSS/sPPEK複合膜材具有最好之電池效能。由上述實驗結果可證明此複合材料對於甲醇燃料電池的應用有其可行性。
並列摘要
Composite proton exchange membranes were prepared from sulfonated poly (phthalazinone ether ketone) (sPPEK) and various amounts of sulfonated polyhedral oligosilsesquioxane (sPOSS). The composite membranes were prepared by casting method with the sulfonated POSS (sPOSS) mixed in sPPEK solution. The chemical structure of the sPOSS was confirmed by FTIR and the degree of sulfonation was identified as 7 % by sulfur content and ion exchange capacity. The membranes were evaluated in terms of thermal stability, water uptake, methanol solution (3M) uptake, bound water ratio, proton conductivity, methanol permeability, and single cell performance. When the degree of sulfonation of sulfonated PPEK was higher, the membrane had higher degree of swilling, but the composite membrane could maintain good dimentional stability. At 80 °C, the water uptake of composite membrane was lower than the original membrane, because the interaction between -SO3H and -OH group decreased the mobility of molecule chains.. The composite membrane contained 5 % sPOSS exhibited the highest proton conductivity of 2.6×10-2 S/cm at 90 °C and 95 % relative humidity, because the sPOSS provide more sulfonic acid group to make more pathway for proton. The composite membranes with various sPOSS content showed lower methanol permeability than the cast Nafion membrane, possibly due to a winding pathway by adding sPOSS for methanol diffusion. The composite 5 % sPOSS/sPPEK membrane showed the highest current density (253mA/cm2) and power density (32 mW/cm2) among all the membranes tested with 3 M methanol in feed at 70 oC.