Nafion®是直接甲醇燃料電池中使用最多的質子交換膜（proton exchange membrane, PEM），其機械和化學穩定性關係著燃料電池的壽命，因此，針對PEM的老化最近做了不少探討。影響PEM老化的因素很多，包括簡單的由膨潤導致的機械老化到複雜的化學反應導致的化學老化以及電池運作過程中產生的電化學老化等。目前已發現電池在運作時，會有少量的H2O2產生且會和Nafion內微量的Fe2+及Cu2+反應產生自由基，它們會攻擊Nafion結構導致老化。這些自由基攻擊的過程的細節尚無全面的圖像。因此，本工作利用NMR光譜和影像並結合SEM、IEC測量等方法對這一過程做進一步的探討。
我們主要利用兩種實驗方式，來模擬Nafion膜在燃料電池運轉中受自由基攻擊後的老化現象。其一 ( Exchange method ) 是將Nafion膜和Fe2+及Cu2+陽離子進行離子交換得到M2+-Nafion膜後再浸泡於H2O2(aq)中，其二 ( Solution method ) 是配製三種不同濃度的Fe2+及Cu2+ Fenton’s solution後再將Nafion膜浸泡其中。而Fe2+及Cu2+會和H2O2(aq)反應產生OH-自由基和O2H-自由基(此反應稱為Fenton’s reaction)來攻擊Nafion使其老化。我們利用SEM觀察膜老化後形貌的變化，利用solid-state及liquid-state 19F NMR觀察化學結構的變化並測量IEC等變化來提供更完整的老化圖像。另外利用鬆弛加權的NMR微影像觀察水的擴散速率的變化，加權微影像可得到各個像素處的擴散速率，從而可以區分膜中不同部位的結構差異。

PEMs degradation can be classified into mechanical, thermal and chemical/electrochemical degradation. The first two are usually responsible for the early stage failure of PEMFCs and they are not a major contribution to the failure of modern fuel cells equipped with perfluorinated PEMs like Nafion® or Dow membrane or other advanced membranes. On the other hand, chemical/electrochemical degradation of PEMs normally proceeds at relatively slow rate. Despite its slow rate, chemical/electrochemical degradation of PEMs is considered to be the most dominant factor of modern fuel cell failure. Chemical/electrochemical degradation of PEMs is attributed to the presence of small amounts of hydroxide radical during long term fuel cell operation. This radical attacks PEM, leading to loss of sulfonic groups and weakening of the cross-linking structure of polymers. The Fenton reaction, which is the reaction between H2O2 and Fe2+ or Cu2+ with hydroxide radicals as its reaction products, is widely served as degradation protocols for accelerated chemical degradation tests of various polymers, including Nafion®.
In this work, we apply two kinds of Fenton reactions, namely, the solution method and the exchange method with Fe2+ and Cu2+ cations. However, we do not follow the routinely used protocol which applies low concentration of cation (16 ppm, in the case of Nafion). Instead, we used a large range of concentration of Fe2+ and Cu2+ (from 16 ppm up to saturation) in order to observe the behavior of Nafion® chemical degradation under miled and harsh environments, and set an upper limit reference of chemical degradation of Nafion® for future works. We use MRI-T1 weighted imaging together with SEM, IEC, 19F MAS NMR and weight loss measurements to investigate chemical degradation of Nafion® 117.

第一章 緒論 1
1.1前言 1
1.2燃料電池簡介 4
1.3 Nafion®薄膜簡介 9
第二章 Nafion®薄膜的老化 13
2.1 Nafion®薄膜的物理老化 13
2.2 Nafion®薄膜的化學老化 15
2.3 Nafion®薄膜化學老化的文獻回顧 18
第三章 利用NMR技術來研究Nafion®老化文獻回顧 28
3.1 In-situ Fuel Cell Degradation Tests22 28
3.2 Ex-situ Degradation under Mimic Fuel Cell Conditions19 31
3.3 Fenton Degradation Tests23 36
第四章 實驗部分 40
4.1實驗材料及藥品 40
4.2實驗樣品前處理及實驗方法 40
4.3實驗樣品分析 43
4.4實驗儀器及工具 45
第五章 結果與討論 46
5.1老化後Nafion®117的質量損失、膜厚度變化、IEC及含水量 46
5.2老化後Nafion®117的IEC及含水量變化 51
5.3老化後Nafion®117的SEM光譜及NMR 微影像實驗 56
5.4老化後Nafion®117的solid-state 19F NMR、liquid-state 19F NMR及1H NMR光譜。 74
5.5 Nafion®117溶液在Fenton’s solution實驗下的老化結果 88
第六章 結論 91
參考文獻 93

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