研究生: |
王鈞顯 Wang, Chun-Hsien |
---|---|
論文名稱: |
利用半開放式化學還原系統製備觸媒於奈米碳管-應用於微型直接甲醇燃料電池 Preparation and catalyst on CNTs by Semi-Reflux-Chemical-Reduction-System-Applied to μDMFC |
指導教授: |
曾繁根
Tseng, Fan-Gang |
口試委員: | |
學位類別: |
碩士 Master |
系所名稱: |
原子科學院 - 工程與系統科學系 Department of Engineering and System Science |
論文出版年: | 2009 |
畢業學年度: | 97 |
語文別: | 中文 |
論文頁數: | 58 |
中文關鍵詞: | 直接甲醇燃料電池 、化學還原 、奈米碳管 |
相關次數: | 點閱:2 下載:0 |
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直接甲醇燃料電池(Direct Methanol Fuel Cell,DMFC)於陽極使用甲醇為燃料,主要是由於其擁有高能量轉換效能,低污染,並可在低溫環境下操作,比之以氫氣做為陽極燃料的質子交換膜燃料電池(Proton Exchange Membrane Fuel Cell,PEMFC) 擁有較方便的燃料儲存、可於室溫操作、運作系統較精簡等優點。未來在攜帶式3C產品上的應用,更顯示甲醇燃料電池有著無限的潛力。
本實驗利用自行研製之化學還原裝置,稱之為「半開放式化學還原系統,Semi-Reflux-Chemical-Reduction System」,能在更短的時間內完成Pt及PtRu觸媒的製備,且具有常壓操作、高溫製程(160℃)及裝置簡單等優點,相較於傳統迴流裝置(Reflux)系統可縮短50%的反應時間,提升觸媒還原的效能。本實驗使用平面Si做為基材,於表面鍍上Ti/Al/Ni三層金屬薄膜,使用Ni做為碳管成長的催化劑,再利用熱化學氣相沉積高溫爐 (Thermal CVD),使用金屬催化熱裂解法(Metal Catalyzed Thermal Chemical Vapor Deposition Method)進行碳管的成長。成長後的碳管經硫酸氧化親水後,利用傅立葉轉換紅外光譜儀(Fourier Transform Infrared Spectroscopy,FTIR)可對其表面官能基做定性分析。再利用上述之化學還原法將Pt前驅物氯鉑酸(H2PtCl6•6H2O)及Ru前驅物氯化銠(III)(RuCl3)和乙二醇(ethylene glycol,EG)的混合溶液,還原成金屬觸媒於碳管表面。乙二醇的作用是做為還原劑,不但具有還原金屬觸媒的效用,同時可穩定金屬觸媒。實驗過程中透過調控H2SO4親水參數,pH值的控制及添加超音波震盪,可獲得顆粒小且分散均勻的Pt奈米觸媒。而調控Pt和Ru的前驅物原子比例和酸鹼值可改變PtRu觸媒分布於碳管表面的粒徑及密度,其CO毒化的抑制能力也會有所改變。觸媒製備完成後,透過循環伏安法(Cyclic Voltammetry)的電化學分析可得知金屬觸媒的活性,掃描式電子顯微鏡(Scanning Electron Microscopy,SEM)及穿透式電子顯微鏡(Transmission Electron Microscpoy,TEM),可以觀察奈米碳管、觸媒在奈米碳管上面的形貌與分佈情形,配合X光能譜分析儀 (Energy Dispersion Spectroscope,EDS)可作為觸媒成分定性分析。最後利用感應耦合電漿質譜儀 (Induced Couple Plasma Mass,ICP-MS)的結果配合電化學量測推算其觸媒的活性定量分析及實際參與反應的表面積。未來將利用X光繞射 (X-ray Diffraction,XRD)圖形分析Pt及PtRu觸媒隨著不同條件之晶格方向變化
研究結果發現,奈米碳管經過H2SO4親水處理之後,膠狀觸媒才有辦法還原於奈米碳管上。利用在親水前的抽氣處理,能提升親水的效能,使得碳管根部亦可有效的沉積金屬觸媒。pH值的控制能改變Pt觸媒的顆粒大小,此結果也於TEM圖中得到證實。超音波的添加可有效改善觸媒還原時於表面的聚集行為。而PtRu觸媒粒徑會隨著pH值的增加而下降,而Pt:Ru原子比越高,觸媒粒徑也會跟著下降,最小顆粒可達1.85奈米,但觸媒顆粒大小和CO毒化抑制的能力間尚須再尋找最佳化的參數。於未來將繼續進行PtRu二元合金之觸媒製備,期望能有效的抑制再氧化峰的形成,並繼續提升其觸媒活性,以達到實際運用於直接甲醇燃料電池的需求。
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