| 摘要: | 一般燃料電池的質子傳導薄膜在應用上最常碰到的問題為在低濕度環境下薄膜保存水的能力不足，導致傳遞質子的水分喪失，進而使得質子導電度下降；另一個問題是質子交換膜應用於直接甲醇燃料電池中時，薄膜有嚴重的甲醇滲透現象，導致在陰極產生混合電位降低電池整體的性能表現。 本研究帶有磺酸根的高分歧結構高分子加入薄膜後，可同時提昇薄膜的質子導電度和大幅降低甲醇滲透率。利用雙馬來醯亞胺(1,1’-(Methylenedi-4,1-phenylene) bismaleimide, BMI)與磺酸化N-苯基馬來醯亞胺(sulfonated N-Phenylmaleimide, sPMI)之共聚高分子與Nafion及磺酸化聚二醚酮(sulfonated poly ether ether ketone, sPEEK)製成複合薄膜， sPMI所帶有的磺酸根增進薄膜的導電度以及藉由高歧狀型態的BMI形成半互穿網絡 (semi-Interpenetrating Polymer Network, semi-IPN) 結構降低甲醇滲透，並以不同的BMI與sPMI比例，調控共聚高分子的型態，製備出能降低甲醇滲透但也有好的質子導電度表現的複合薄膜。 由實驗得知，在BMI : sPMI = 1 : 4時所製備的薄膜，無論在sPEEK薄膜或是Nafion薄膜上，都能有效的降低甲醇的滲透。在20%1B4P的sPEEK薄膜其甲醇滲透可達10-7cm2/s；Nafion方面，N-1B4P-24hr薄膜甲醇滲透也能降低至純Nafion的三分之一。而在質子導電度方面，10%1B1P的sPEEK薄膜在100℃時的變濕導電度也高於原本的sPEEK薄膜；在Nafion薄膜中，除了sPMI比例較低的N-4B1P-6hr及N-4B1P-24hr兩薄膜在100℃時的變濕導電度較不及純Nafion外，其他4種組成的薄膜則是優於純Nafion薄膜。而其他如離子交換容量(Ion Exchange Capacity, IEC)、水含量(Water uptake)及熱穩定性等性質，在本篇論文中皆有加以探討、比較。 The most common problems of the fuel cell membranes are the insufficient of the ability to retain water at low humidity that result in the low proton conductivity and on the other hand, the high methanol permeability that deduces the performance of the fuel cell. Because of the morphology of the water channel, the most commonly used commercial Nafion membrane has high rate of soaking and losing water. Therefore, the proton conductivity of Nafion membranes is pretty low under ambient condition. On the other hand, the hydrocarbon proton conducting membranes may have lower proton permeability but the proton conductivity may not be good enough compared to Nafion membrane. This research introduce the hyperbranch copolymer with sulfonic groups into membranes can promote proton conductivity and reduce methanol permeability simultaneously. We use the copolymer of 1,1’-(Methylenedi-4,1-phenylene) bismaleimide (BMI) and sulfonated N-Phenylmaleimide (sPMI) into Nafion and sulfonated poly ether ether ketone (sPEEK). The proton conductivity will increase by the sulfonic groups of the sPMI and the methanol permeability will decrease by the formation of semi-IPN (semi-Interpenetrating Polymer Network) structure of BMI. The different ration between BMI and sPMI can adjust the structure of semi-IPN in order to prepare an organic/organic composite membrane that has high proton conductivity under low humidity and high methanol resistant ability. According to the data, we know that while the ratio between BMI and sPMI is 1 : 4, the methanol permeability is effectively decreased in spite of sPEEK and Nafion membranes. The methanol permeability of 20%1B4P sPEEK membrane can reach 10-7cm2/s and N-1B4P-24hr membrane can deduce 1/3 compared to the pure Nafion. The proton conductivity of 10%1B1P sPEEK membrane is higher than pure sPEEK under 100℃ and various humidity. On the other side, except the N-4B1P-6hr and N-4B1P-24hr with fewer sulfonic groups, the proton conductivity of the rest 4 membranes with different composition are better than pure Nafion under 100℃ and various humidity. The Ion Exchange Capacity (IEC), water uptake and the thermal stability are also discussed in the research. |
