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研究生:林建亨
研究生(外文):Chien-Heng Lin
論文名稱:奈米甲醇過濾層改善DMFC性能之研究
論文名稱(外文):Study on the performance improvement of DMFC by two nano methanol filter Layers in PEM
指導教授:萬傑豪
指導教授(外文):Chieh-Hao Wan
學位類別:碩士
校院名稱:明道管理學院
系所名稱:材料暨系統工程研究所
學門:工程學門
學類:材料工程學類
論文種類:學術論文
論文出版年:2006
畢業學年度:94
語文別:中文
論文頁數:62
中文關鍵詞:直接甲醇燃料電池甲醇竄透奈米觸媒甲醇過濾層化學植入-還原法
外文關鍵詞:DMFCmethanol crossovernano catalyst、methano
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摘要

目前,直接甲醇燃料電池(DMFC)仍存在陽極電催化動力學較弱、CO毒化觸媒與甲醇竄透(Methanol cross-over)的問題,於是許多研究透過高活性奈米觸媒與多層觸媒結構設計來改善這些問題,其中奈米觸媒被視為改善甲醇電催化動力學較弱與利用率的有效方案。
本研究於PEM陽極製作奈米Pt-Ru或Pt粒子層作為甲醇過濾層,並結合直印法,設計4組陽極觸媒層的MEA,以改善甲醇竄透及甲醇利用率,進而提昇DMFC的性能與可靠度。利用SEM、EPMA與X-ray測試分析化學植入-還原法沉積的Pt-Ru 合金或Pt奈米層的微結構形態、相態、合金成份比例及含量與奈米層厚度,並以CO2氣體偵測器測量氧氣端CO2的出口量,利用恆定電位/電流儀測試不同觸媒層結構的活性表面積,利用燃料電池測試台測定電極極化曲線。
由SEM與 EPMA的結果顯示,適當控制化學植入-還原法製程參數,可於PEM表面製作ㄧ連續Pt或Pt-Ru奈米粒子層。奈米Pt或Pt-Ru粒子大小約10nm,並經由特性測試顯示,此奈米Pt或Pt-Ru層可產生約0.85V電位(OCV)及電流。所獲得奈米Pt-Ru合金粒子層由於具有大表面積、不同金屬互溶性高與高觸媒活性等特性,已滿足作為可快速反應竄透至PEM的甲醇觸媒層,而表現出甲醇過濾層的功能。由實驗證實,PEM 內奈米金屬觸媒層可有效抗甲醇竄透率達50%,其中雙層觸媒層的Ru 合金原子比必須大於50%,才能表現出最佳抗甲醇竄透效果。
Abstract

Presently, direct methanol fuel cell still has the problems of poorer electro-catalysis kinetic at anode, poisoning of catalyst by CO and methanol crossover. To ameliorate these problems, much recently afford has devoted to the study of the nano catalyst, which own the high catalyst activity and specific surface electron structure, and the multi-catalyst layer structure design. Among them, the nano catalyst is regarded as the efficacious method to enhance the electro-catalysis kinetic and the fuel utilization at anode.
This study prepares two nano Pt-Ru alloy or Pt particles layer in PEM anode side as the methanol filter layer by using the impregnation-reduction (IR) method. By combination of the novel directed-printing method, we design eight types of anode catalyst layer to meet the problems of methanol crossover as well as the fuel utilization. And thus this enhances the DMFC performance and reliability. SEM, EPMA and X-ray are used to analyze the microstructures, morphology, compositions, distributions, thickness and phases of the resulted nano Pt-Ru alloy or Pt particles layer. The CO2 sensor is used to detect the CO2 contents in the output oxygen stream. Potentialstat/Galvanostat is adopted to measure the electro-active surface area (EASA) for the proposed catalyst layer structures. Fuel cell test station is applied to test the I-V curves of the MEAs.
The SEM , EPMA and X-ray results show that we can obtain the nano Pt-Ru alloy or Pt particles layer in PEM anode side by appropriately selected process parameters. The resulted Pt-Ru alloy or Pt particles size is approximately 10nm. This nano Pt-Ru alloy catalyst possess extremely large surface area and highly miscibility between metal as well as the catalyst activity. Accordingly, this characteristic fulfills the requirement for the high degree of oxidation activity for methanol crossover in the PEM. This owns the functions of filter out methanol instantly. The results prove that the nano Pt-Ru alloy catalyst layer efficiently declines the methanol crossover to 50% as compared to the MEA without the nano Pt-Ru alloy catalyst layer in PEM. The best tolerance ability to the methanol crossover is obtained at the Ru atom ratio greater than 50% in the double nano Pt-Ru alloy catalyst layer.
目錄
第一章 緒論............................................................................................01
1-1 前言...........................................................................................01
1-2 直接甲醇燃料電池的介紹.......................................................03
1-3 甲醇於陰極Pt電極上之氧化機制...........................................05
1-4 研究動機...................................................................................07
第二章 文獻回顧....................................................................................09
第三章 實驗方法....................................................................................20
3-1 實驗藥品及材料.......................................................................20
3-2 實驗設備與分析儀器...............................................................21
3-3 實驗方法...................................................................................22
3-3-1 質子交換膜前處理........................................................22
3-3-2化學植入還原法之製備..................................................22
3-3-3 直印法製作導電子觸媒層............................................22
3-3-4 網印法製作觸媒層.......................................................23
3-3-5 熱壓法...........................................................................23
3-3-6 分析儀器.......................................................................24
第四章 結果與討論................................................................................28
4-1 於PEM表面還原時間對陽極奈米觸媒層成長機制的影響.28
4-1-1 5min還原時間沈積的Pt40-Ru60觸媒層.......................28
4-1-2 20min還原時間沈積的Pt40-Ru60觸媒層......................28
4-1-3 比較還原時間5min、20min觸媒層............................28
4-1-4 化學植入-還原法沉積觸媒層成長機制......................29
4-2. PEM表面Pt-Ru/Pt雙層奈米觸媒層的製作..........................35
4-2-1. 內層為Pt,外層是Pt40-Ru60的雙層觸媒層沈積…..35
4-2-2. 內層為Pt,外層是Ru的雙層觸媒層沈積……..….35
4-3. 設計4組奈米甲醇過濾層結合直印法的MEA性能……..38
4-3-1. 微結構分析…………………………………………..39
4-3-1-1. X光繞射(XRD)分析…………………………….39
4-3-1-2. Auger電子能譜儀分析………………………….39
4-3-1-3. 場發射電子微探儀分析……….………………..39
4-3-1-4. 恆定電位/電流儀(Potentialstat)分析……………40
4-3-2. 各MEA以H2為燃料的極化曲線…….…………….47
4-3-3. 各樣品以CH3OH為燃料的性能曲線………………48
4-3-4.各樣品甲醇竄透量…………………………………….51
第五章 結論............................................................................................57
第六章 未來工作及建議........................................................................58
參考文獻..................................................................................................59

圖目錄
圖1-1 直接甲醇燃料電池示意圖…………………………………04
圖1-2 陽極觸媒吸附示意圖………………………………………04
圖1-3 IR法結合直印法觸媒層示意圖……………………………08
圖2-1 化學植入-還原法示意圖…………………………………...19
圖2-2 多層觸媒結構電極示意圖…………………………………19
圖3-1 化學植入-還原法示意圖…………………………………...25
圖3-2 化學植入還原法製之自製反應裝置………………….…....26
圖3-3 膜電極組之製作流程圖………………………………..…...27
圖4-1 5min還原時間的Pt-Ru沉積層表面SEM圖…………….30
圖4-2 5min還原時間的Pt-Ru沉積層截面EPMA圖……………31
圖4-3 5min還原時間的Pt-Ru觸媒層截面Mapping..…………..31
圖4-4 20min還原時間的Pt-Ru沉積層表面SEM圖……………32
圖4-5 20min還原時間的Pt-Ru沉積層截面EPMA圖…………...33
圖4-6 20min還原時間的Pt-Ru觸媒層截面Mapping…………..33
圖4-7 PEM表層之Pt與Ru離子還原成Pt與Ru金屬成長機制…34
圖4-8 雙層Pt40-Ru60/Pt奈米觸媒層示意圖………………………35
圖4-9 雙層Ru/Pt奈米觸媒層示意圖……………………………..35
圖4-10 雙層Pt40-Ru60/Pt奈米觸媒層截面的EPMA圖…………..37
圖4-11 雙層Ru/Pt奈米觸媒層截面的EPMA圖…………………37
圖4-12 以IR法製得純Pt、Ru與Pt-Ru合金的XRD繞射圖譜…40
圖4-13 以IR法製得Pt60-Ru40的Auger圖譜……………………..41
圖4-14 以IR法製得Pt40Ru60的Auger圖譜………………………41
圖4-15 以IR法製得Pt20Ru80的Auger圖譜………………………42
圖4-16 雙層Pt40-Ru60/Pt60-Ru40奈米觸媒層截面的EPMA圖……43
圖4-17 雙層Pt40-Ru60/ Pt40-Ru60奈米觸媒層截面的EPMA圖…..43
圖4-18 雙層Pt40-Ru60/Pt20-Ru80奈米觸媒層截面的EPMA圖……44
圖4-19 以H2為燃料測得各樣品C.V圖..........................................45
圖4-20 以CH3OH為燃料測得各樣品的C.V圖..............................46
圖4-21 以H2為燃料測得各樣品的I-V 曲線圖..............................47
圖4-22 以CH3OH為燃料於50℃測得各樣品的I-V 曲線圖..........49
圖4-23 以CH3OH為燃料於60℃測得各樣品的I-V 曲線圖..........49
圖4-24 以CH3OH為燃料於80℃測得各樣品的I-V 曲線圖..........50
圖4-25 各樣品於50℃的甲醇竄透CO2濃度(ppm)隨時間變化圖..52
圖4-26 各樣品於60℃的甲醇竄透CO2濃度(ppm)隨時間變化圖..52
圖4-27 各樣品於80℃的甲醇竄透CO2濃度(ppm)隨時間變化圖..53
圖4-28 各樣品於50℃的甲醇竄透速率圖…………........................54
圖4-29 各樣品於60℃的甲醇竄透速率圖…….…….......................55
圖4-30 各樣品於80℃的甲醇竄透速率圖…………........................56





表目錄
表1-1 比較4組陽極觸媒層MEA………………………………..08
表3-1 實驗藥品及材料……………………………………………20
表3-2 實驗設備……………………………………………………21
表3-3 實驗分析儀器………………………………………………21表4-1 本研究MEA的負載量………………………………….…38
表4-2 以H2為燃料測得各樣品的電極活性表面積…………..…45
表4-3 以CH3OH測得各樣品電極活性表面積………………..…46
表4-4 IR法MEA於CH3OH (2M)燃料下與對照組性能比較表...50
表4-5 IR法MEA於CH3OH (3M)燃料下與對照組性能比較表...50
表4-6 不同比例觸媒層的抗甲醇(50℃)竄透改變率………......…54
表4-7 不同比例觸媒層的抗甲醇(60℃)竄透改變率….…….....…55
表4-8 不同比例觸媒層的抗甲醇(80℃)竄透改變率….…….....…56
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