隨著氣候變遷及新興與發展中國家的經濟及人口增長，全球水資源風險日益上升，對許多原本就缺乏淡水的國家而言，海水淡化成為重要開發技術，近年來出現一種新穎的海水淡化技術-電容去離子(capacitive deionization, CDI)，是一種利用電吸附程序去除水中離子的技術，相較於其他傳統海水淡化技術，具低成本，低耗能等優勢，其基本原理是在兩電極間施加一電場，使帶電荷之離子吸附於相反電荷之電極表面，藉以達到去除水中離子的目的。
　　石墨烯特殊的二維結構於奈米技術領域，被視為具有吸引力之材料之一；鐵奈米顆粒於環境工程已有廣泛應用，若能結合環境友善的鐵與良好導電性之石墨烯，可用以提升電容去離子效率。本研究中鐵奈米顆粒成功摻雜於石墨烯中，利用X-ray繞射儀、掃描式電子顯微鏡、穿透式電子顯微鏡以及接觸角測定儀來觀察複合材料表面特性，並進一步運用電化學儀器測試(循環伏安法、計時電位法、計時電流法以及阻抗分析)分析複合材料之電化學特性。
　　氧化石墨烯(graphene oxide (GO))以改良式Hummer’s法製備，選用還原劑Dithionite還原GO生成rGO。研究中添加環境友善之鐵金屬，使用水熱合成法(Ex-situ)、In-situ 原位合成與Fe@C奈米核殼材料三種方法改質石墨烯；水熱合成法(Ex-situ)為使用已還原好之石墨烯加入鐵鹽，並在高溫高壓下製成Fe/rGO複合材料；In-situ法則是使用氧化石墨烯於不添加還原劑情況下，利用亞鐵離子被氧化，而氧化石墨烯同步被還原為石墨烯形成Fe/rGO複合材料；此外，添加Fe@C核殼顆粒形成Fe@C/rGO複合材料，三種方法皆可提升電極之比電容，比電容與未改質的rGO相比，從原始rGO的 42.19 F/g，三種方法在最佳配比狀況下，分別提升至169.3 F/g、141.56 F/g、186.88 F/g，而比電容的增加主要是因為鐵金屬的法拉第虛擬電容(Faradic pseudocapacitance)所貢獻，最後將三種複合材料應用於CDI系統，進行鹹水中NaCl之離子分離研究。

Due to climate change and population growth in developing countries, the risk of lacking water resource is increasing globally. For many water-scarce countries, seawater desalination has become an important technology. In recent years, there is a novel desalination technology ─ capacitive deionization (CDI), which is a technique for removing ions from water by electrosorption. Compared with other traditional seawater desalination technology, it has advantages of  low cost and low energy consumption. The basic principle of CDI is to apply an electric field between two electrodes, so that the charged ions can be adsorbed on the opposite charge of the electrode surface to achieve the removal of water ions.
  Graphene with unique two-dimensional structure is one of the attractive material  in  nanotechnology . The iron nanoparticles have been widely used in environmental engineering. If graphene could combine with environmentally benign iron, it will enhance the efficiency of capacitive deionization. In this study, iron nanoparticles were successfully doped within graphene, and the surface characteristics of the composites were observed by X-ray diffraction, Scanning Electron Microscope, Transmission Electron Microscopy and contact angle. The electro-chemical properties of the composites were also analyzed by electrochemical analyzer (Cyclic Voltammetry, Chronopotentiometry, Chronoamperometry and Electrochemical Impedance Spectroscopy).         
  Graphene oxide (GO) was prepared by modified Hummer's method, and reduced by Dithionite to produce graphene (rGO). The additions of environmental friendly iron with graphene were synthesized by hydrothermal method (Ex-situ), In-situ synthesis and mixing with Fe@C core-shell nanoparticles. For hydrothermal synthesis (Ex-situ), graphene and iron salt with high temperature and pressure were synthesized to yieldFe/rGO composite materials; For In-situ method, the preparation of iron nanoparticles/graphene composites was conducted with ferrous serving as reductant to reduce GO. In this in-situ procedure, ferrous is oxidized to ferric and GO is reduced to rGO simultaneously. In addition, the addition of Fe@C core-shell particles to graphene to prepare Fe@C/rGO composites. Three methods with the best ratio can enhance the specific capacitance from 42.19 F/g (original rGO) to 169.3 F/g (ex-situ), 141.56 F/g (in-situ), 174.04 F/g (Fe@C). The increase of specific capacitance is due to the ferrous metal faradic pseudocapacitance contribution. Finally, desalination with three composites in CDI System were compared.

第一章	研究緣起與目的	1
1.1	研究緣起	1
1.2	研究目的	1
第二章	文獻回顧	3
2.1	海水淡化技術	3
2.1.1	多效蒸發法(MED)	4
2.1.2	多級閃化法(MSF)	6
2.1.3	逆滲透法(RO)	8
2.1.4	電透析法(ED)	8
2.1.5	電容去離子法(CDI)	9
2.2	電容去離子技術	11
2.2.1	電容去離子技術發展之簡介	11
2.2.2	電容去離子技術之原理	13
2.3	電容去離子之電極種類	14
2.3.1	活性碳	14
2.3.2	碳氣凝膠	15
2.3.3	奈米碳管	17
2.3.4	石墨烯	18
2.4	奈米電極材料之合成	21
2.4.1	原位沉積法	21
2.4.2	水熱合成法	22
2.5	法拉第電流	24
2.5.1	過渡金屬氧化物	24
第三章	實驗設備與方法	25
3.1	實驗架構	25
3.2	實驗藥品與設備	27
3.2.1	實驗藥品	27
3.2.2	實驗設備	29
3.3	電極材料之製作	30
3.3.1	氧化石墨烯(Graphene Oxide, GO)之製備	30
3.3.2	還原氧化石墨烯(Reduced Graphene Oxide, rGO)之製備	32
3.3.3	添加鐵改質石墨烯	34
3.3.4	儀器分析方法	39
3.3.4.1	X-ray 繞射儀(XRD)	39
3.3.4.2	掃描式電子顯微鏡(SEM)	39
3.3.4.3	穿透式電子顯微鏡(TEM)	40
3.3.4.4	接觸角測定儀(Contact angle analyzer)	41
3.3.4.5	循環伏安法 (Cyclic Voltammetry, CV)	42
3.3.4.6	Chronopotentiomatry	44
3.3.4.7	Chronoamperometry	44
3.3.4.8	Electrochemical Impedance Spectrum	44
3.4	電容去離子實驗 (CDI System)	45
第四章	結果與討論	47
4.1	Ex-situ水熱合成Fe/rGO複合材料應用於CDI	47
4.1.1	Ex-situ水熱合成Fe/rGO複合材料表面特性分析	47
4.1.2	Ex-situ水熱合成Fe/rGO複合材料電化學分析	53
4.1.3	Ex-situ水熱合成Fe/rGO複合材料應用於電容去離子	60
4.2	In-situ Fe/rGO複合材料應用於電容去離子	62
4.2.1	In-situ Fe/rGO複合材料表面特性分析	62
4.2.2	In-situ Fe/rGO複合材料電化學分析	70
4.2.3	In-situ Fe/rGO複合材料應用於電容去離子	78
4.3	Fe@C/rGO複合材料應用於電容去離子	80
4.3.1	Fe@C/rGO複合材料表面特性分析	80
4.3.2	Fe@C/rGO複合材料電化學分析	84
4.3.3	Fe@C/rGO複合材料電容去離子應用	94
4.4  鐵氧化物比電容之比較  96
第五章	結論與建議	98
第六章	Reference	100

 
IV
List of Figure
Figure 2.1.1.1 Ratio of desalination technology ............................................ 3
Figure 2.1.2.1 Schematic diagram of the MED plant at PSA (Alberto de la
Calle et. al., 2014). ................................................................................. 5
Figure 2.1.2.2MSF desalination process. Note: S.P., set point; Comp.,
comparator.............................................................................................. 7
Figure 2.1.5.1Purification (a) and regeneration (b) processes in CDI ......... 10
Figure 2.2.1.1 Timeline of scientific developments of CDI, indicating
milestones since the inception of CDI in 1960. (S. Porada et., 2013) . 12
Figure 2.3.4.1 SEM images of PG (a, b) and NG (c, d) at low and high ..... 19
Figure 2.4.1.1Schematic of the synthesis of rGO/Fe3O4NCs. ..................... 21
Figure 2.4.2.1 Schematic illustration for the formation mechanism of
CuFe2O4 / rGO. .................................................................................... 22
Figure 2.4.2.2 TEM images of CuFe2O4 / RGO prepared at different
reaction temperatures： (A, B) 130 ℃, (C, D) 180 ℃..................... 23
Figure 2.4.2.1 Schematic experimental structure for CDI system ............... 26
Figure 3.3.1.1 Graphene oxide (GO) preparation procedure. ...................... 31
Figure 3.3.2.1 Graphene (rGO) preparation procedure................................ 33
Figure 3.3.3.1 In-situ procedure for preparation of Fe/rGO. ....................... 36
Figure 3.3.3.2 Procedure for preparation of Fe@C/rGO ............................. 38
Figure 3.3.4.5.1 Cyclic Voltammetry ........................................................... 43
Figure 3.3.4.8.1 Schematic diagram of CDI system .................................... 46
Figure 4.1.1.1 XRD patterns of (a) GO, (b) rGO, and (c) Fe/rGO (Hthermal)
................................................................................................ 49
Figure 4.1.1.2 FESEM images of the (a, b) graphene generated by dithionite
V
reduction, (c, d, e) Fe/rGO (H-thermal) (f) EDS of the Fe/rGO (Hthermal)
................................................................................................ 50
Figure 4.1.1.3 TEM images of the (a, b)Fe/rGO (H-thermal) (c) EDS of the
Fe/rGO (H-thermal) ............................................................................. 51
Figure 4.1.1.4 Contact angle images of the (a) graphene generated by
dithionite, (b) Fe/rGO (H-thermal) ...................................................... 52
Figure 4.1.2.1 Cyclic voltammograms for the (a) graphene, (b) Fe/rGO (Hthermal),
............................................................................................... 54
Figure 4.1.2.2 Charge-discharge curves of (a) graphene, (b) Fe:rGO (Hthermal),(
c)graphene and Fe/rGO(H-thermal) ..................................... 57
Figure 4.1.2.3 The current-time response obtained at applied cyclic potential
on graphene and Fe/rGO composites. .................................................. 58
Figure 4.1.2.4 The electrochemical impedance spectra (EIS) measured at
frequency range of 100 kHz to 0.01 Hz for the obtained electrodes :
graphene, Fe:rGO (H-thermal)............................................................. 59
Figure 4.2.1.1 XRD patterns of (a) GO, (b) rGO, (c) Fe/rGO (condition
1),(d) Fe/rGO (condition 2), and (e) Fe/rGO (condition 3) ................. 63
Figure 4.2.1.2 FE-SEM images of (a) rGO, (b) Fe/rGO condition 2 (x50K),
and (c) Fe/rGO condition 2 (x100K), (d) EDX of Fe/rGO condition 2
.............................................................................................................. 64
Figure 4.2.1.3 TEM images of (a) rGO, (b) and (c) Fe/rGO (condition 2) .. 65
Figure 4.2.1.4 (a) FE-SEM image of Fe/rGO and selected area of EDX (b)
selected area 4 (c) selected area 5, and (d) selected area 6 .................. 67
Figure 4.2.1.5 Contact angle image of (a)rGO, (b)Condition 1, (c)Condition
2, (d)Condition 3 .................................................................................. 68
VI
Figure 4.2.2.1 Cyclic voltammetry (a) rGO, (b) Fe/rGO (condition 1), (c)
Fe/rGO (condition 2) , and (d) Fe/rGO (condition 3). ......................... 71
Figure 4.2.2.2 Mass normalized specific capacitance (F/g) of rGO, Fe/rGO
(condition 1), Fe/rGO (condition 2), and Fe/rGO (condition 3) with
respect to various scan rates. ................................................................ 72
Figure 4.2.2.3 Charge-discharge curves of (a) rGO, (b) Fe/rGO (condition
1), (c) Fe/rGO (condition 2), (d) Fe/rGO (condition 3) under various
current density, and (e) comparison of all electrodes at current density
of 1 A/g ................................................................................................ 75
Figure 4.2.2.4 The current-time response obtained at applied cyclic potential
on (a) graphene, Fe/rGO (condition 1), Fe/rGO (condition 2), Fe/rGO
(condition 3), and (b) enlarge image of selected area. ......................... 76
Figure 4.2.2.5 The electrochemical impedance spectra (EIS) measure at
frequency range of 100KHz to 0.01Hz for graphene, Fe/rGO
(condition 1), Fe/rGO (condition 2), and Fe/rGO (condition 3). ......... 77
Figure 4.3.1.1 FESEM images of the (a, b) graphene generated by dithionite
reduction, (c, d, e, f ) Fe@C:rGO (1:5) with various magnification. .. 81
Figure 4.3.1.2 TEM images of the (a, b) Fe@C:rGO (1:5), (c) EDX of
Fe@C:rGO (1:5), (d) selected area electron diffraction (SAED) pattern
of Fe:rGO (1:5) .................................................................................... 82
Figure 4.3.1.3 Contact angle images of the (a) graphene generated by
dithionite reduction, (b) Fe@C:rGO (1:5), (c) Fe@C:rGO (1:10), (d)
Fe@C:rGO (1:50). ............................................................................... 83
Figure 4.3.2.1 Cyclic voltammograms for the (a) graphene, (b) Fe@C:rGO
(1:5), (c) Fe@C:rGO (1:10), and (d)Fe@C:rGO (1:50). ..................... 87
VII
Figure 4.3.2.2 Capacitance retention of Fe/graphene in the potential range
of 0~0.8 V at the scan rate of 1, 5,10, 50, 100 mV/s. .......................... 89
Figure 4.3.2.3 Charge-discharge curves of the (a) graphene, (b) Fe@C:rGO
(1:5), (c) Fe@C:rGO (1:10), and (d) Fe@C:rGO (1:50) under different
current densities. .................................................................................. 90
Figure 4.3.2.4 Charge-discharge curves for the graphene, Fe@C:rGO (1:5),
Fe@C:rGO (1:10), and Fe@C:rGO (1:50) at current density of 1 A/g.
.............................................................................................................. 91
Figure 4.3.2.5 The current-time response obtained at applied cyclic potential
on the surface of graphene, Fe@C:rGO (1:5), Fe@C:rGO (1:10), and
Fe@C:rGO (1:50). ............................................................................... 92
Figure 4.3.2.6 The electrochemical impedance spectra (EIS) measure at
frequency range of 100 KHz to 0.01 Hz for graphene, Fe@C:rGO
(1:5), Fe@C:rGO (1:10), Fe@C:rGO (1:50) ....................................... 93
VIII
List of Table
Table 2.3.2-1 adsorption of Carbon aerogel in Colorado river water .......... 16
Table 3.2.1-1 Manufacturers and purity of experimental medicines ........... 27
Table 4.2.1-1 Contact angle of graphene and Fe/rGO composites .............. 69
Table 4.2.2-1 Specific capacitance (F/g) of rGO, Condition 1, Condition 2,
Condition 3........................................................................................... 73
Table 4.3.2-1Mass normalized specific capacitance (F/g) of graphene,
Fe@C:rGO (1:5), Fe@C:rGO (1:10), and Fe@C:rGO (1:50). ............ 88
Table 5.1 Mass normalized specific capacitance (F/g) of graphene, ex-situ
Fe/rGO (H-thermal)、in-situ Fe/rGO (condition 2) and Fe@C/rGO
(1:5) composites with respect to the scan rates. ................................... 99

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