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研究生： 陳鵬宇
Chen, Peng-Yu
論文名稱： 環狀及鏈狀電解質薄膜內奈米尺度電滲透與輸送現象分子動力分析
Molecular Dynamics Analysis of Nano-scale Electro-osmotic and Transport Phenomena inside Ring- and Chain-type Electrolytic Membranes
指導教授： 洪哲文
Hong, Che-Wun
口試委員:
學位類別： 博士
Doctor
系所名稱： 工學院 - 動力機械工程學系
Department of Power Mechanical Engineering
論文出版年： 2009
畢業學年度： 97
語文別： 英文
論文頁數： 84
中文關鍵詞： 分子動力模擬 、電滲透 、直接甲醇燃料電池 、甲醇穿透 、電場效應 、磺酸化聚醚醚酮酮膜
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    • 本研究執行分子動力模擬藉以分析環狀鏈狀電解質薄膜內奈米尺度電滲透現象，目標是想要解決直接甲醇燃料電池內的甲醇穿透問題。論文中主要是利用分子動力學的手段分析奈米尺度的輸送現象以及研究相關的效應。
    本論文首先研究電場效應對於Nafion膜內輸送動力學的影響，沿著質子傳遞的方向施加不同的電場，其強度由2.5×103 V m-1到7.5×103 V m-1。模擬結果發現，當考慮電場時，膜的形態會產生明顯的變化；隨著電場強度增加，質子以及水分子的移動性也會增加。而從分子的移動軌跡圖可以看出施加電場以及沒有施加電場兩者輸送現象的差異，此外我們可以利用這個分子分析技術研究在電場的影響下水分子簇的分佈及其大小。
    由擴散及滲透機制造成的甲醇穿透會降低直接甲醇燃料電池的性能。本論文第二部份將由原子的觀點重現Nafion膜內甲醇穿透現象，在四種不同的甲醇濃度下，模擬由Nafion、水分子以及質子所構成的系統。模擬結果顯示甲醇分子會隨著水分子以及質子經由磺酸根在電解質內移動。不同甲醇濃度下甲醇的電滲透拖曳係數以及擴散係數皆已被求得並且與實驗值比較，而熱效應對於甲醇擴散的影響也經由此分子分析技術加以研究。
    本論文的第三部份則是利用同樣的原子模擬技術研究分子構造效應對於Nafion膜以及磺酸化聚醚醚酮酮(SPEEKK)膜內輸送動力學的影響。模擬的系統是由聚合物電解質、質子及包含水和甲醇的溶劑分子所組成。模擬結果顯示含水的SPEEKK膜會比Nafion膜擁有較少的親疏水性相分離，並且SPEEKK膜內形成的水通道也會比Nafion膜內的水通道狹窄。這些特性會造成水分子以及質子在SPEEKK膜內的移動性較低且因此降低了甲醇的擴散係數，進而減少直接甲醇燃料電池內甲醇滲透問題。

    Abstract I Table of Content V List of Figures VIII List of Tables XII Nomenclature XIII Chapter 1 Introduction 1 1.1 Background 1 1.2 Introduction to DMFC 2 1.3 Objectives and Motivation 4 1.4 Literature Survey 5 1.4.1 Experimental and Theoretical Studies on Nafion Membrane 5 1.4.2 Experimental and Theoretical Studies on Methanol Crossover 6 1.4.3 Experimental and Theoretical Studies on SPEEKK Membrane 8 Chapter 2 Molecular Modeling and Simulation 10 2.1 Molecular Modeling 10 2.1.1 Nano-scale Transport Dynamics inside a Hydrated Nafion Membrane with Electric Field Effects 10 2.1.2 Molecular Analysis on Methanol Diffusion in a Model Nafion Membrane 12 2.1.3 Molecular Structure and Transport Dynamics in Nafion and SPEEKK Membranes 14 2.2 Molecular Simulation 16 2.2.1 Inter-molecular Potential Function 18 2.2.2 Intra-molecular Potential Function 19 2.3 Computer Simulation 21 Chapter 3 Results and Discussions 24 3.1 Nano-scale Transport Dynamics inside a Hydrated Nafion Membrane with Electric Field Effects 24 3.1.1 System Equilibration 24 3.1.2 Membrane Morphology Analysis 26 3.1.3 Molecular Structure Analysis 29 3.1.4 Molecular Mobility Analysis 34 3.1.5 Water Cluster Analysis 38 3.2 Molecular Analysis on Methanol Diffusion in a Model Nafion Membrane 40 3.2.1 System Equilibration 40 3.2.2 Molecular Structure Analysis 42 3.2.3 Electro-osmotic Analysis 49 3.2.4 Molecular Diffusion Analysis 50 3.2.5 Transport Trajectory Analysis 54 3.2.6 Thermal Effect analysis 56 3.3 Molecular Structure and Transport Dynamics in Nafion and SPEEKK Membranes 58 3.3.1 System Equilibration 58 3.3.2 Membrane Morphology Analysis 60 3.3.3 Molecular Structure Analysis 62 3.3.4 Molecular Mobility Analysis 68 3.3.5 Methanol Crossover Analysis 71 Chapter 4 Conclusions 73 4.1 Nano-scale Transport Dynamics inside a Hydrated Nafion Membrane with Electric Field Effects 73 4.2 Molecular Analysis on Methanol Diffusion in a Model Nafion Membrane 74 4.3 Molecular Structure and Transport Dynamics in Nafion and SPEEKK Membranes 74 4.4 Recommendations of Future Work 75 References 77

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