電容去離子為一具發展性的脫鹽技術，藉由施加電壓使多孔性碳材的電雙層電容進行可逆的離子吸/脫附行為，其裝置簡單、能耗低及脫鹽效率高，解決了傳統脫鹽技術在半鹹水處理上的問題。活性碳為常見的電極材料，具有比表面積高且成本低的優點，然而在不當的條件下操作，尤其是電位窗位置，會產生許多法拉第反應，使去離子效能衰減並加速電極老化，故須對電極材料進行最佳化來達到最佳的去離子效能；其疏水及導電性差的特性也限制了其表現，故利用氮摻雜的方式改善，並增加其電荷吸/脫附能力以提升去離子效能。
首先在第一部分，本研究對活性碳進行最佳化探討，藉由定電流充/放電曲線與充放電時間比找出最佳工作電位範圍(0.7 V~ -0.5 V vs. Ag/AgCl wire)，並以電量平衡算出最佳正/負極質量比為1:1，最佳外加電壓時間為10分鐘，在18圈1.2 V/0 V充放電循環下呈穩定的脫鹽量12.9 mg/g、電荷效率為0.81，有效減緩副反應造成的衰減現象。
在第二部分我們以三聚氰胺作為氮源，藉酸洗及熱處理的方式合成氮摻雜活性碳並作為正極，探討其對去離子效能及長時間穩定性的影響，結果顯示其親水性、導電性有顯著提升，且其表面負電荷是影響離子吸脫附的關鍵；由於許多離子尚未排出電極，延長放電時間有助於脫鹽量的提升；在100圈的充放電循環下，NAC30//AC仍保有最大脫鹽量的40%，並有效延緩了正極的氧化現象。

Capacitive deionization (CDI) is a promising desalination technology. By applying a voltage, the electrical double-layer constructed within porous carbon materials will conduct the reversible ion adsorption/desorption process. Owing to its simple device structure, low energy consumption and high desalination efficiency, CDI circumvents the problems of traditional desalination technologies in the brackish water treatment. Activated carbon (AC) is a common material for the CDI electrodes because of its advantages of high specific surface area and low cost. While the improper operation conditions, especially the position of working potential window, will generate many Faradaic reactions, which will cause the decay of CDI performance and accelerate the aging of electrodes. Thus, it’s crucial to conduct parameter optimization of the electrode material to achieve its best desalination performance. Also, its hydrophobic property and poor conductivity limit the CDI performance. Therefore, we introduced nitrogen atoms to improve these problems and the ion adsorption/desorption ability of AC to enhance CDI performance.
In the first part, this work focused on the parameter optimization of activated carbon-based CDI system. The optimized working potential range was found to be from 0.7 V to -0.5 V (vs. Ag/AgCl wire) via the charging-discharging curves and the ratios of charging/discharging time. The best mass ratio of positive/negative electrodes by charge balance was 1:1. The best duration time of applying voltage was 10 min. The CDI results showed a stable desalination performance at a cell voltage of 1.2 V in 18 charging/discharging cycles with a salt adsorption capacity of 12.9 mg/g and a charge efficiency of 0.81. This optimization method effectively reduced the decay of CDI performance caused by side reactions.
In the second part, we synthesized nitrogen-doped activated carbon by acid pre-treatment and thermal annealing of activated carbon and melamine, where melamine acted as the nitrogen source. The as-prepared N-doped carbon was served as positive electrode to investigate its effects on desalination performance and the stability under long-term operation. The results showed that these samples had improved hydrophilicity and electrical conductivity. Also, the surface negative charge was the key factor to affect ion adsorption/desorption. Since a lot of ions remained in the electrodes, prolonging the discharging time could result in the enhancement of salt adsorption capacity. After 100 charging/discharging cycles, NAC30//AC still remained 40% of its maximum salt adsorption capacity and effectively reduced the corrosion of positive electrodes.

摘要 I
Abstract II
誌謝 IV
目錄 VI
圖目錄 X
表目錄 XV
第一章 簡介及理論基礎 1
1-1 電化學及電雙層基礎 1
1-1-1 電化學反應系統 1
1-1-2 電雙層電容器及其理論 3
1-2 電容去離子技術基礎與應用 6
1-2-1 電容去離子技術原理及應用 6
1-2-2 電容去離子技術之發展及改良 8
1-2-3 與傳統去離子技術比較 10
1-2-4 影響去離子效能之因素 11
1-3 電容去離子系統之電極 15
1-3-1 電極種類及裝置結構 15
1-3-2 常見之電極材料與特性 18
1-3-3 長時間操作下之電極效能衰減 19
1-3-4 活性碳改質方法 20
1-4 氮摻雜碳材應用於電容去離子系統 22
1-4-1 氮摻雜碳材對去離子效能之影響 22
1-4-2 氮摻雜碳材之合成 24
1-5 研究動機與實驗架構 26
第二章 實驗方法與儀器 28
2-1 實驗藥品與儀器 28
2-1-1 實驗藥品 28
2-1-2 實驗儀器 28
2-2 電極製備方式 30
2-2-1 鈦片基材處理及活性碳清洗 30
2-2-2 氮摻雜活性碳材料之合成 30
2-2-3 工作電極之製備 31
2-3 三極式電化學系統 32
2-3-1 自製銀/氯化銀參考電極之方法 32
2-3-2 三極式電化學系統裝置 32
2-3-3 開路電位測試 (Open Circuit Potential, OCP) 33
2-3-4 循環伏安法 (Cyclic voltammetry, CV) 34
2-3-5 計時電位分析法 (Chronopotentiometry, CP) 35
2-3-6 電化學阻抗圖 (Electrochemical impedance spectroscopy, EIS) 36
2-4 兩極式電容去離子系統 37
2-4-1 電量平衡法 37
2-4-2 電容去離子實驗與模組 37
第三章 活性碳材料與電化學分析 39
3-1 自製銀/氯化銀參考電極之穩定性測試 39
3-2 不同活性碳之電容去離子效能 40
3-3 ACS25活性碳材料鑑定 42
3-3-1 材料表面分析(BET、XPS、接觸角) 42
3-3-2 材料電化學分析(EIS、OCP、CV、CP) 45
3-4 ACS252電極之工作電位窗 48
3-4-1 以循環伏安法(CV)測定最大工作電位窗範圍 48
3-4-2 以計時電位分析法(CP)測定最佳工作電位窗範圍 49
3-5 ACS25電極於電量平衡雙極式電容去離子系統之探討 52
3-5-1 電量平衡法及最佳外加電壓時間 52
3-5-2 外加電壓大小對去離子效能之影響 54
3-5-3 最佳操作條件下之去離子效能長時間穩定性 56
3-6 結論 58
第四章 氮摻雜活性碳(NAC)的合成及去離子效能 59
4-1 氮摻雜活性碳材料鑑定 60
4-1-1 材料表面分析(BET、XPS、接觸角) 60
4-1-2 材料電化學分析(EIS、CV、CP) 64
4-2 NAC之去離子效能 66
4-2-1 含氧官能基對氮摻雜之影響 66
4-2-2 電極表面負電荷對去離子效能之影響 68
4-2-3 放電時間對離子吸附之影響 70
4-3 長時間操作之穩定性 73
4-3-1 NAC30之長時間操作穩定性 73
4-3-2 對稱式系統 76
4-4 結論 79
第五章 總結與未來展望 80
5-1 總結 80
5-2 未來展望 82
第六章 參考文獻 84
 

1. 胡啟章, 電化學原理與方法. 2002, 五南圖書出版股份有限公司.
2. Nomoto, S., et al., Advanced capacitors and their application. Journal of power sources, 2001. 97: p. 807-811.
3. Zhang, L.L. and X.S. Zhao, Carbon-based materials as supercapacitor electrodes. Chemical Society Reviews, 2009. 38(9): p. 2520-2531.
4. Faulkner, A.J.B.a.L.R., Electrochemical Methods: Fundamentals and applications, 2nd ed. 2001, New York: John Wiley & Sons Inc.
5. Oren, Y., Capacitive deionization (CDI) for desalination and water treatment — past, present and future (a review). Desalination, 2008. 228(1): p. 10-29.
6. Anderson, M.A., A.L. Cudero, and J. Palma, Capacitive deionization as an electrochemical means of saving energy and delivering clean water. Comparison to present desalination practices: Will it compete? Electrochimica Acta, 2010. 55(12): p. 3845-3856.
7. Porada, S., Zhao, R., Van Der Wal, A., Presser, V., & Biesheuvel, P. M., Review on the science and technology of water desalination by capacitive deionization. Progress in Materials Science, 2013. 58(8): p. 1388-1442.
8. Johnson, A.M. and J. Newman, Desalting by Means of Porous Carbon Electrodes. Journal of The Electrochemical Society, 1971. 118(3): p. 510-517.
9. Biesheuvel, P.M. and A. van der Wal, Membrane capacitive deionization. Journal of Membrane Science, 2010. 346(2): p. 256-262.
10. Li, H. and L. Zou, Ion-exchange membrane capacitive deionization: A new strategy for brackish water desalination. Desalination, 2011. 275(1): p. 62-66.
11. Min, B.H., J.-H. Choi, and K.Y. Jung, Improvement of capacitive deionization performance via using a Tiron-grafted TiO2 nanoparticle layer on porous carbon electrode. Korean Journal of Chemical Engineering, 2018. 35(1): p. 272-282.
12. Liu, Y., et al., Enhanced desalination efficiency in modified membrane capacitive deionization by introducing ion-exchange polymers in carbon nanotubes electrodes. Electrochimica Acta, 2014. 130: p. 619-624.
13. Gao, X., et al., Surface charge enhanced carbon electrodes for stable and efficient capacitive deionization using inverted adsorption–desorption behavior. Energy & Environmental Science, 2015. 8(3): p. 897-909.
14. Wu, T., et al., Highly Stable Hybrid Capacitive Deionization with a MnO2 Anode and a Positively Charged Cathode. Environmental Science & Technology Letters, 2018. 5(2): p. 98-102.
15. Kang, J., et al., Comparison of salt adsorption capacity and energy consumption between constant current and constant voltage operation in capacitive deionization. Desalination, 2014. 352(Supplement C): p. 52-57.
16. He, D., et al., Faradaic Reactions in Water Desalination by Batch-Mode Capacitive Deionization. Environmental Science & Technology Letters, 2016. 3(5): p. 222-226.
17. Mossad, M. and L. Zou, A study of the capacitive deionisation performance under various operational conditions. Journal of Hazardous Materials, 2012. 213-214: p. 491-497.
18. Yeh, C.-L., et al., Improved performance in capacitive deionization of activated carbon electrodes with a tunable mesopore and micropore ratio. Desalination, 2015. 367: p. 60-68.
19. Suss, M., et al., Water desalination via capacitive deionization: what is it and what can we expect from it? Energy & Environmental Science, 2015. 8(8): p. 2296-2319.
20. Remillard, E.M., et al., A direct comparison of flow-by and flow-through capacitive deionization. Desalination, 2018. 444: p. 169-177.
21. Pasta, M., et al., A Desalination Battery. Nano Letters, 2012. 12(2): p. 839-843.
22. Jeon, S.-i., et al., Desalination via a new membrane capacitive deionization process utilizing flow-electrodes. Energy & Environmental Science, 2013. 6(5): p. 1471-1475.
23. Farmer, J.C., et al., Capacitive Deionization of NaCl and NaNO3 Solutions with Carbon Aerogel Electrodes. Journal of The Electrochemical Society, 1996. 143(1): p. 159-169.
24. Xu, P., et al., Treatment of brackish produced water using carbon aerogel-based capacitive deionization technology. Water Research, 2008. 42(10): p. 2605-2617.
25. Aslan, M., et al., Improved capacitive deionization performance of mixed hydrophobic/hydrophilic activated carbon electrodes. Journal of Physics: Condensed Matter, 2016. 28(11): p. 114003.
26. Duan, F., et al., Desalination stability of capacitive deionization using ordered mesoporous carbon: Effect of oxygen-containing surface groups and pore properties. Desalination, 2015. 376: p. 17-24.
27. Wang, L., et al., Capacitive deionization of NaCl solutions using carbon nanotube sponge electrodes. Journal of Materials Chemistry, 2011. 21(45): p. 18295-18299.
28. Yang, Z.Y., et al., Sponge‐templated preparation of high surface area graphene with ultrahigh capacitive deionization performance. Advanced Functional Materials, 2014. 24(25): p. 3917-3925.
29. Zhang, L., et al., Cocoon derived nitrogen enriched activated carbon fiber networks for capacitive deionization. Journal of Electroanalytical Chemistry, 2017. 804: p. 179-184.
30. Cohen, I., et al., Enhanced Charge Efficiency in Capacitive Deionization Achieved by Surface-Treated Electrodes and by Means of a Third Electrode. The Journal of Physical Chemistry C, 2011. 115(40): p. 19856-19863.
31. Lu, D., W. Cai, and Y. Wang, Optimization of the voltage window for long-term capacitive deionization stability. Desalination, 2017. 424: p. 53-61.
32. Xie, Z., et al., Polydopamine Modified Activated Carbon for Capacitive Desalination. Journal of The Electrochemical Society, 2017. 164(12): p. A2636-A2643.
33. Huang, W., et al., Desalination by capacitive deionization process using nitric acid-modified activated carbon as the electrodes. Desalination, 2014. 340: p. 67-72.
34. Lee, B., et al., Enhanced Capacitive Deionization by Dispersion of CNTs in Activated Carbon Electrode. ACS Sustainable Chemistry & Engineering, 2018. 6(2): p. 1572-1579.
35. Alencherry, T., et al., Effect of increasing electrical conductivity and hydrophilicity on the electrosorption capacity of activated carbon electrodes for capacitive deionization. Desalination, 2017. 415: p. 14-19.
36. Yan, T., et al., Ion-selective asymmetric carbon electrodes for enhanced capacitive deionization. RSC Advances, 2018. 8(5): p. 2490-2497.
37. Ismagilov, Z.R., et al., Structure and electrical conductivity of nitrogen-doped carbon nanofibers. Carbon, 2009. 47(8): p. 1922-1929.
38. Chen, T., et al., Porous nitrogen-doped carbon microspheres as anode materials for lithium ion batteries. Dalton Transactions, 2014. 43(40): p. 14931-14935.
39. Li, Y., et al., Design of nitrogen-doped cluster-like porous carbons with hierarchical hollow nanoarchitecture and their enhanced performance in capacitive deionization. Desalination, 2018. 430: p. 45-55.
40. Wen, Z., et al., Crumpled nitrogen‐doped graphene nanosheets with ultrahigh pore volume for high‐performance supercapacitor. Advanced Materials, 2012. 24(41): p. 5610-5616.
41. Chen, L.-F., et al., Synthesis of Nitrogen-Doped Porous Carbon Nanofibers as an Efficient Electrode Material for Supercapacitors. ACS Nano, 2012. 6(8): p. 7092-7102.
42. Liu, Y., et al., Nitrogen-doped porous carbon spheres for highly efficient capacitive deionization. Electrochimica Acta, 2015. 158: p. 403-409.
43. Xu, X., et al., Enhanced capacitive deionization performance of graphene by nitrogen doping. Journal of Colloid and Interface Science, 2015. 445: p. 143-150.
44. Liu, Y., et al., Nitrogen-doped carbon nanorods with excellent capacitive deionization ability. Journal of Materials Chemistry A, 2015. 3(33): p. 17304-17311.
45. Li, Y., et al., High performance capacitive deionization using modified ZIF-8-derived, N-doped porous carbon with improved conductivity. Nanoscale, 2018. 10(31): p. 14852-14859.
46. Zhao, S., et al., High capacity and high rate capability of nitrogen-doped porous hollow carbon spheres for capacitive deionization. Applied Surface Science, 2016. 369: p. 460-469.
47. Porada, S., et al., Capacitive Deionization using Biomass‐based Microporous Salt‐Templated Heteroatom‐Doped Carbons. ChemSusChem, 2015. 8(11): p. 1867-1874.
48. Seredych, M., et al., Surface functional groups of carbons and the effects of their chemical character, density and accessibility to ions on electrochemical performance. Carbon, 2008. 46(11): p. 1475-1488.
49. Yasin, A.S., et al., Fabrication of N-doped &SnO2-incorporated activated carbon to enhance desalination and bio-decontamination performance for capacitive deionization. Journal of Alloys and Compounds, 2017. 729: p. 764-775.
50. Liu, N.-L., et al., ZIF-8 Derived, Nitrogen-Doped Porous Electrodes of Carbon Polyhedron Particles for High-Performance Electrosorption of Salt Ions. Scientific Reports, 2016. 6: p. 28847.