電容去離子系統是一項可解決傳統脫鹽技術之處理程序複雜且能量損耗大的去離子技術。電容去離子技術是透過活性碳電容器於水相電解液的電雙層電容特性，使活性碳電極在充、放電過程中具備可逆的吸、脫附離子能力。然而在實際的電容去離子系統中，除了非法拉第反應外，仍可能產生多項法拉第反應，造成整體系統的效能降低。相較於傳統作法偏向以低操作電壓1.2 V的方式避免法拉第反應的發生，本研究將藉由成本低的活性碳材料探討電容去離子系統的最適化電位窗條件。
本論文第一部分主要藉由三極式電化學反應系統了解活性碳(ACS679)於濃度8 mM氯化鈉水溶液下的電化學性質。首先，量測其開環路電壓為0.05 V (vs. Ag/AgCl)及最大化的電位窗範圍為-1.15 V ~ 0.85 V (vs. Ag/AgCl)；並以電量平衡概念計算出正/負極重量比為4.6:1所組裝的活性碳電容器，以定電壓充電-放電方法及監控系統驗證正/負極電位範圍，在施加電壓2 V、放電電壓0 V且18圈連續充放電實驗結果得知平均鹽類吸附容量為10.52 mg g-1、庫倫效率為48.8 %、能量損耗為197.7 kJ mol-1。為了要進一步提升庫倫效率，降低不必要的損耗，因此必須了解實際系統中發生的法拉第反應，故以旋轉環-盤電極量測氧氣還原反應電位為-0.4 V (vs. Ag/AgCl)，且在-0.57 V (vs. Ag/AgCl)時有一半機率會產生四個電子轉移的氧氣還原反應。
第二部分為找出活性碳的最適化電位窗範圍。藉由定電壓持續三分鐘遞增法，發現不同的正/負極重量比在不同的電壓下有各自最佳的鹽類吸附容量。接著，藉由三極式電化學系統中的定電流充放電法，找出活性碳在充電與放電時間比例趨近於1.12的電位窗範圍為-0.6 V ~ 0.8 V (vs. Ag/AgCl)。藉由電量平衡公式計算出兩極的重量比為1:1.4，施加電壓1.4 V應用於電容去離子系統，其平均鹽類吸附容量為11.86 mg g-1、庫倫效率為62 %、能量損耗為108.8 kJ mol-1。相較之下，施加電壓減少卻得到更高的鹽類吸附容量、庫倫效率以及較低的能量損耗。

Common electrode materials in capacitive deionization (CDI) system are activated carbons (ACs) with the advantages of low cost and high specific surface area, which are suitable for adsorbing/desorbing ions reversibly. However, there possibly exists several Faradaic reactions in the CDI systems under the real operation conditions. The higher voltage is applied, the more faradaic reactions occurs, resulting in the poor charge and energy efficiencies, but a low cell voltage of a CDI system usually leads to a low deionization capacity. Accordingly, the most important thing is to find a suitable potential window for the electrode materials with high charge and energy efficiencies.
The first part of this thesis is to identify the electrochemical properties of the ACS679-coated electrode by a three-electrode system. The open circuit potential is 0.05 V (vs. Ag/AgCl) with a potential window between -1.15 V ~ 0.85 V (vs. Ag/AgCl) without significant water decomposition. The mass ratio of the negative to positive electrodes on the basis of the charge balance methodology is 4.6:1, which shows an average salt adsorption capacity of 10.52 mg/g under a charge efficiency of 48.8 % and energy consumption of 197.7 kJ/mol at 2.0 V. Furthermore, the oxygen reduction reaction (ORR) for the AC-coated electrode in the 8 mM NaCl solution was detected by the rotating ring-disk electrode voltammetry, which started to significantly occur at -0.4 V (vs. Ag/AgCl). The methodology for varying the mass ratio of positive to negative electrodes, such as: 1:1 and 4.6:1, are systematically compared by monitoring the variations in pH and hydrogen peroxide concentration in the 8 mM NaCl solution to confirm the potential reactions, such as the oxygen evolution reaction (OER) and ORR.
The second part of this thesis is to find the optimal potential window for AC-coated electrodes in the CDI system. Here, we use the three-electrode system to find the optimal potential window, -0.6 V ~ 0.8 V (vs. Ag/AgCl), for the CDI system with the AC-coated electrodes by means of the galvanostatic charge-discharge curves when the charge time/discharge time ratio is approximately equal to 1.12. The mass ratio according to the charge balance is 1:1.4, which shows a higher salt removal capacity of 11.86 mg/g, a higher charge efficiency of 62 % and a lower energy consumption of 108.8 kJ/mol in comparison of the CDI system with the positive to negative electrode ratio of 4.6:1 at the largest cell voltage of 2.0 V.

中文摘要 I
ABSTRACT III
誌謝 V
目錄 VII
圖目錄 XI
表目錄 XV
第一章 緒論及理論基礎 1
1-1 電化學原理 1
1-1-1 電化學反應系統 1
1-1-2 參考電極的功能與應用 3
1-2 電雙層電容器 5
1-2-1 電雙層理論 7
1-2-2 電雙層重疊現象 9
1-3 電容去離子技術基礎與應用 10
1-3-1 簡介與發展 10
1-3-2 原理 12
1-3-3 與傳統去離子技術比較 13
1-3-4 電極材料與特性 14
1-3-5 參考電極之應用 17
1-3-6 施加電壓及電位窗之影響 18
1-3-7 法拉第反應於電容去離子系統 20
1-4 研究動機及實驗架構 24
第二章 實驗方法與儀器介紹 27
2-1 實驗藥品與儀器介紹 27
2-1-1 實驗藥品 27
2-1-2 實驗儀器 28
2-2 電極製備方式 29
2-2-1 鈦片基材預處理 29
2-2-2 活性碳清洗方法 29
2-2-3 活性碳工作電極之製備 29
2-3 電化學分析實驗 30
2-3-1 三極式電化學系統裝置 30
2-3-2 電容去離子系統裝置 31
2-3-3 銀/氯化銀參考電極之製備 34
2-3-4 開環路電壓測試 (Open Circuit Potential, OCP) 34
2-3-5 循環伏安法 (Cyclic voltammetry, CV) 34
2-3-6 定電流充放電法 (Chronopotentiometry, CP) 35
2-3-7 安培分析法 (Amperometry, i-t curve) 36
2-3-8 旋轉-環盤電極(RRDE)與線性掃描伏安法 37
2-4 以紫外光-可見光(UV-VIS)檢驗過氧化氫濃度 38
2-5 材料分析儀器介紹 40
2-5-1 比表面積與孔徑分析儀(Surface area and porosity analyzer) 40
2-5-2 X射線電子能譜儀(X-ray photoelectron spectroscopy, XPS) 43
第三章活性碳材料與電化學分析 44
3-1 活性碳之材料鑑定 44
3-1-1 氮氣吸脫附曲線之表面積與孔洞分析 44
3-1-2 X射線電子能譜儀之表面官能基分析 45
3-1-3 界面電位之測定 46
3-2 銀/氯化銀參考電極之穩定性測試 47
3-3 單極式活性碳之電化學特性分析 49
3-3-1 開環路電壓法 50
3-3-2 以循環伏安法測定工作電位窗範圍 51
3-3-3 以定電流充放電法測定工作電位窗範圍 52
3-3-4 以旋轉環-盤電極測定氧氣還原電位 54
3-3-5 活性碳電極於CDI系統之法拉第反應機制 56
3-4 探討雙極式活性碳電極應用於電容去離子系統 57
3-4-1 探討不同活性碳重量比對pH之影響 60
3-4-2 探討不同活性碳重量比對過氧化氫產生量之影響 62
3-5 結論 63
第四章 探討不同活性碳重量比對CDI系統最適化電位窗之影響 65
4-1 以電化學方法探討多種正/負極重量比與電壓之關係 65
4-1-1 探討不同電壓對導電度之影響 65
4-1-2 探討不同電位窗對pH之影響 67
4-1-3 探討不同電位窗對電容去離子效能之影響 72
4-2 以三極式電化學系統探討不同電位窗下充放電時間比 74
4-3 最適化正/負極電位窗應用於電容去離子系統 76
4-3-1 調整正/負極電位窗驗證最適化電位窗範圍 78
4-4 結論 80
第五章 總結與未來展望 82
5-1 總結 82
5-2 未來展望 86
參考文獻 87

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