本研究旨在發展低溫操作用的直接甲醇燃料電池(Direct methanol fuel cell, DMFC)電解質，以取代價格昂貴又無法有效阻擋甲醇穿透的Nafion膜材。本研究採用成膜性高、具良好化學穩定性且低價格的聚乙烯醇( Polyvinyl alcohol, PVA)為膜材主體，而分成兩個系統來探討。一是改質PVA有機膜，利用氯磺酸作磺酸化反應，接著以戊二醛行交鏈反應，另一為先將PVA磺酸化後，再添加無機的四乙基矽烷(Tetraethoxysilane, TEOS)及磷酸三甲酯(Trimethyl phosphate, TMP)，使其分散於PVA結構中，並在酸性觸媒的催化下，進行溶膠-凝膠(sol-gel)反應，以合成SPVA/SiO2/P2O5有機/無機複合膜。並對開發的膜材作一系列性質分析及研究，包括結構、含水率、熱性質分析、導電率、甲醇滲透度等。結果顯示，改質的CSPVA-30-1h薄膜，在30oC且含水的狀態下，氫離子導電度可達2.89x10-3 S/cm，而就甲醇滲透度的結果，以CSPVA-45-3h表現最佳，於30oC下為3.26x10-7 cm2/s，約為Nafion甲醇滲透度的十分之一，顯示改質後的膜材，確實有阻擋甲醇滲透的能力。在有機/無機複合膜(SPVA/SiO2/P2O5)中, 其氫離子導電度以SPSP-612-1h表現最佳，可達5.3x10-3 S/cm，且在75oC、80% HR條件下，可達1.0x10-2 S/cm。
本研究亦嘗試建立膜特性與膜之氫離子導電度及甲醇滲透率之關係。

The aim of this study was to develop new proton exchange membranes for low temperature DMFC for the substitution of the Nafion membrane showing high cost and poor barrier to methanol crossover. Because of its good chemical stability, film-fabrication ability and low cost, PVA was chosen to be the matrix of developed membranes. There were two systems developed in this study. One is a modified PVA membrane cross-linked and sulfonized with glutaraldehyde and chlorosulfonic acid, respectively. The other is an organic-inorganic hybrid PVA membrane in which PVA sulfonated with chlorosulfonic acid is organic matrix and then inorganic matrix was formed from the reaction between Tetraethoxysilane (TEOS) and Trimethyl phosphate (TMP). Various analysis techniques were used to characterize the structure and study the physical and thermal properties, proton conductivity as well as methanol permeability of the developed membranes. The CSPVA-30-1h membrane showed the best proton conductivity of 2.89x10-3 S/cm among the modified PVA membranes at 30 oC in flooded state. The methanol permeability of the CSPVA-45-3h membrane was measured to be 3.26x10-7 cm2/s about one order less than that of the Nafion membrane. It was found that a significant reduction in methanol crossover could be achieved using the modified PVA membrane. Among the organic-inorganic hybrid membranes, SPVA/SiO2/P2O5, the best proton conductivity was obtained to be 5.3x10-3 S/cm for the SPSP-612-1h membrane at 30 oC in flooded state. In addition, higher proton conductivity of ~1.0x10-2 S/cm could be achieved at 75 oC and 80% R.H.
The relationship between the characteristics and the proton conductivity as well as the methanol permeability for the developed membranes is also discussed in this study.

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