臺灣博碩士論文加值系統

近三十年來，全釩氧化還原液流電池(Vanadium Redox Flow Battery, VRFB)備受矚目，因其具有可深度放電、自放電低、安全性高搭配設計靈活之優點，且可隨著設置場所不同而改變其設計。本論文研究目的針對石墨氈電極材料進行表面改質，其方法利用熱處理以及酸處理之方式，並利用熱重量分析儀、全自動程序溫控化學吸脫附分析儀、場發射掃描式電子顯微鏡、比表面吸分析儀、X射線光電子能譜儀、接觸角量測儀、循環伏安測試、交流阻抗分析以及全電池測試對石墨氈進行探討其表面性質及其電化學性能之影響。
經由熱重分析曲線與程序溫控氧化曲線分析後，可知熱處理對石墨氈在溫度上面有其極限，500 ˚C是在大氣下熱處理之最高溫，而太低溫無法產生熱處理效果。從SEM與BET分析可知，熱處理有助於對表面造成微蝕，配合BET分析可得知，微蝕所造成的微孔有助於提高比表面積，且以500 ˚C下熱處理三小時的比表面積為最高，約為53.06 m2/g。再經由XPS分析發現，經由熱處理後，石墨氈表面之氧化物被清除，且經由酸處理後，在O1s的圖譜上可明顯看出酸處理有助於增加O在表面的含量。在電化學行為上，熱處理後可以降低極化現象，且在酸處理後，更趨於明顯，藉由交流阻抗分析可知，酸處理後的石墨氈在電荷轉移阻抗較單純熱處理後小，搭配半電池性能測結果可推斷處理後之石墨氈有助於增加反應可逆性，經全電池在電流密度為100 mA/cm2充放電後得知，經400 ˚C熱處理兩天及酸處理之效果為最好，其能量效率為63.94 %，且有效電容量為18 AhL-1。
經由以上結果發現，熱處理可以清除石墨氈可增加反應面積並提升能量效率，而在酸處理後可在石墨氈上大幅增加C-OH，由此C-OH鍵結可使活性物質與電極更直接的進行電子轉移並減少固液相間阻抗並提升有效電容量。

In recent years vanadium redox flow battery (VRFB) has received considerable attention because its outstanding features such as safety, flexible design, long cycle life and high reliability. As in other batteries, electrode is the key factor of energy efficiency. The purpose of this study is to investigate the effect of modified graphite felt on the electrochemical performance for vanadium redox flow battery. From the result of thermogravimetric analysis (TGA) and auto catalyst characterization system (TPO), it is found that the best appropriated heat treatment temperature is in the range of 400 to 600°C. The structure, composition, specific surface area, and electrochemical properties of the graphite felt which treated by heat and acid were characterized using scanning electron microscopy (SEM), Nitrogen adsorption-desorption isotherm, X-ray photoelectron spectroscopy (XPS), contact angle, cyclic voltammetry (CV), and charge-discharge test. From the SEM images and specific surface area result, it was found that the surface area of the graphite felt increases after heat treatment. The surface of graphite felt carries more hydrophilic groups, such as –OH after acid treatment. The hydrophilic groups improve the redox reaction of vanadium ions, thereby increase the efficiency of the vanadium redox flow battery. The coulombic, voltage, energy efficiencies, and specific capacity of the graphite felt after heat treatment at 400°C for 2 days and acid treatment respectively are 96.62%, 65.99%, 63.94%, and 18 AhL-1 at 100 mA.

目錄

摘要 I
Abstract II
致謝 III
目錄 IV
圖目錄 VII
表目錄 X
第1章、 前言 1
1.1 緒論 1
1.2 液流電池 4
第2章、 文獻回顧 5
2.1 液流電池發展歷史 5
2.1.1 The iron-chromium redox system 5
2.1.2 Zinc/bromine redox flow cells 6
2.1.3 All vanadium redox flow battery(VRB) 6
2.1.4 Bromine/polysulphide flow battery 7
2.1.5 Zinc/cerium redox flow cells 7
2.1.6 The vanadium-bromine redox system 8
2.2 全釩氧化還原液流電池工作原理 10
2.3 全釩氧化還原液流電池關鍵材料 12
2.3.1 電解液 14
2.3.2 離子交換膜 15
2.3.3 雙極板 16
2.3.4 電池電極 17
第3章、 研究動機與目的 19
3.1 研究目的 19
第4章、 實驗方法與步驟 21
4.1 實驗器材 21
4.1.1 化學藥品及材料 21
4.1.2 實驗器材及設備 22
4.2 實驗架構 23
4.3 實驗步驟 24
4.3.1 前處理 24
4.3.2 熱處理 24
4.3.3 酸處理 25
4.3.4 電解液製備 26
4.3.5 半電池測試之極片製作與組裝 26
4.4 儀器分析 27
4.4.1 熱重量分析儀(Thermal gravity Analysis, TGA) 27
4.4.2 程序溫控氧化反應(TPO) 27
4.4.3 場發射掃描式電子顯微鏡(FE-SEM) 27
4.4.4 比表面積分析儀(BET) 28
4.4.5 X射線光電子能譜儀(XPS) 28
4.4.6 接觸角量測儀(Contact angle) 28
4.5 電化學性能測試 29
4.5.1 半電池循環伏安測試(Cyclic Voltammetry) 29
4.5.2 交流阻抗分析 29
4.5.3 單電池充放電測試 30
第5章、 結果與討論 31
5.1 石墨氈材料性質分析 31
5.1.1 熱處理對石墨氈性能的影響 31
5.1.2 場發射式電子掃描顯微鏡分析(FE-SEM) 34
5.1.3 比表面積分析(BET) 37
5.1.4 X射線光電子能譜(XPS) 39
5.1.5 接觸角量測 49
5.2 石墨氈電化學性能分析 52
5.2.1 半電池循環伏安測試(Cyclic Voltammetry) 52
5.2.2 交流阻抗分析(A.C. Impedance) 57
5.2.3 單電池充放電測試(Charge-Discharge) 62
第6章、 結論 69
第7章、 參考文獻 71


圖目錄
Figure 2 1 Redox flow systems (a) bromine/polysulphide, (b) vanadium/vanadium, (c) vanadium/bromide, (d) iron/chromium with anionic membrane, (e) iron/chromium with cationic membrane, and (f) zinc/bromide.[9] 9
Figure 2 2 Unit redox flow cell for energy storage[9] 11
Figure 2 3 The single cell structure of all-vanadium redox flow battery.[19] 13
Figure 4 1 石墨氈表面改質流程圖 23
Figure 5 1 Weight loss of the graphite felt at various temperatures. 32
Figure 5 2 Temperature-Programmed Oxidation of the graphite felt in 2% O2+He atmosphere. 33
Figure 5 3 The SEM micrographs of the graphite felt：(a)Untreated, (b)400˚C for 2 days and (c)500˚C for 3 hours. (At 5,000X magnification ). 35
Figure 5 4 The SEM micrographs of the graphite felt：(a)Untreated, (b)400˚C for 2 days and (c)500˚C for 3 hours. (At 20,000X magnification ). 36
Figure 5 5 XPS spectra of the untreated graphite felt：(a) the survey spectra, (b) core level spectra of the C1s region and (c) core level spectra of the O1s region. 40
Figure 5 6 XPS spectra of the graphite felt heat treated at 400˚C for 2 days：(a) the survey spectra, (b) core level spectra of the C1s region and (c) core level spectra of the O1s region. 41
Figure 5 7 XPS spectra of the graphite felt heat treated at 500˚C for 3 hours：(a) the survey spectra, (b) core level spectra of the C1s region and (c) core level spectra of the O1s region. 42
Figure 5 8 XPS spectra of the graphite felt heat treated at 400˚C for 2 days and after Fenton reagent ：(a) the survey spectra, (b) core level spectra of the C1s region and (c) core level spectra of the O1s region 43
Figure 5 9 XPS spectra of the graphite felt heat treated at 500˚C for 3 hours and after Fenton reagent：(a) the survey spectra, (b) core level spectra of the C1s region and (c) core level spectra of the O1s region. 44
Figure 5 10 XPS core level spectra of O1s region for the graphite felt heated. 45
Figure 5 11 The contact angle of the graphite felt：(a)Untreated, (b)400˚C for 2 days, (c)500˚C for 3 hours, (d)400˚C for 2 days after Fenton reagent, and (e)500˚C for 3 hours after Fenton reagent. 50
Figure 5 12 The CV curves of the graphite felt (a)untreated, (b)400˚C for 2 days and (c)after Fenton reagent treated recorded at different scan rates in 0.1 M VOSO4 + 20 wt% H2SO4 solution. 53
Figure 5 13 The CV curves of the graphite felt (a)untreated, (b)500˚C for 3 hours and (c)after Fenton reagent treated recorded at different scan rates in 0.1 M VOSO4 + 20 wt% H2SO4 solution. 54
Figure 5 14 The CV curves of the graphite felt recorded at 10 mVs-1 scan rates in 0.1 M VOSO4 + 20 wt% H2SO4 solution. 55
Figure 5 15 Nyquist plot of the graphite felt at the polarization potential of 0.95 V. 58
Figure 5 16 Nyquist plot of the graphite felt treated at the polarization potential of 0.95 V. 59
Figure 5 17 The equivalent circuit of diagram. 60
Figure 5 18 Charge-discharge curves of the graphite felt for untreated at various current densities. 64
Figure 5 19 Charge-discharge curves of the graphite felt (a) 400°C for 2 days and (b) after Feton reagent treated at various current densities. 65
Figure 5 20 Charge-discharge curves of the graphite felt (a) 500°C for 3 hours and (b) after Feton reagent treated at various current densities. 66
Figure 5 21 The specific capacity of graphite at 100 mAcm-2 67
 
表目錄

Table. 1 1 Comparison of technicalities of different energy storage devices as against the redox flow battery[8] 3
Table. 4 1實驗藥品名稱、化學式及其相關資料 21
Table. 4 2實驗儀器名稱及其相關資料 22
Table. 5 1 Specific surface areas of the graphite felts after different heat treatment. 38
Table. 5 2 General spectra of major elements for different graphite felts peak area percentage. 46
Table. 5 3 General spectra of major elements for different graphite felts peak area percentage 47
Table. 5 4 Curve-fit data of O1s spectra. 48
Table. 5 5 The contact angle of the graphite felt. 51
Table. 5 6 The parameters obtained from the CV curves on the defferent graphite felt elecrodes at 10 mVs-1 scan rates. 56
Table. 5 7 Parameters obtained from fitting the impedance. 61
Table. 5 8 Efficiency values of graphite felt under various current densities. 68

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