Content of Figures

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Abstract

In this study, hydrous ruthenium oxide was deposited on titanium and carbon nanotube substrate by cathodic deposition method. The cathodic deposition method to produce hydrous ruthenium oxides coatings was found more effective and fast.

Combination of amorphous and nano crystalline structure of hydrous ruthenium oxide was investigated by high resolution electron microscopy. Thin and uniform layer of hydrous ruthenium oxide coating can be deposited on carbon nanotube substrate. The thickness of the coating layer was found less than 10 nm. The coating layer of hydrous ruthenium oxide was comprised nano-crystalline grain and amorphous structure, and the nano sized was about 2 nm. The atomic arrangement of ruthenium oxide which deposited on the surface of carbon nanotubes were almost appeared to be Ru and RuO₂. The characteristics of hydrous ruthenium oxide were be investigated by XRD, XPS, TGA.

Adding carbon nanotube not only can increase the capacity, but also enhance the efficiency of deposition processes. The hydrous ruthenium oxides can be deposited on Ti substrate as short as 5 minutes of deposition period. The electrical capacity characteristics of the deposits were examined by cyclic voltammetry. Effects of capacitance and microstructure upon deposition conditions and additional various treatments on coating were also observed. The capacitances of specimens without or with carbon nanotube additive and with dispersed carbon nanotube additive were 428 F/g, 590 F/g, and 718.8 F/g in this study. The consumption of coating was found very effective for this specimen after 10⁵ charge/discharge cycles which lead to the tremedenously decreasing in the measured capacitance.

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Acknowledgement

經過了漫長的十一年時光，學士四年，碩士兩年，博士五年，我終於也要離開這多年的生活之地-中華大學。回想一下剛進來的模樣，從充滿慌張的小伙子，

到現在可以獨當一面的小大人，也漸漸的開始略有長進。大學剛畢業時，我順利地考進研究所，繼續留下來唸書。身邊的同學，一個個的離開，取而代之的，是新的同學，實驗室的學長，指導我的指導教授，以及工研院的各位同仁們。很快的碩士兩年時光又過去，同學一個個的離開學校去業界尋求發展。學校只剩我一個人繼續往這研究之路邁進，身邊也無陪伴的學術同伴，學校與工研院就成了我在新竹的唯一庇護。然而很多次有著休學的念頭，煩躁的想法，這時家人就會適時的跳出來挺住我，讓我的學術之路不那麼孤單。還記得每天一大早跟老師 Meeting 的時光，然後就往工研院騎車過去，開始實驗，週而復始。一年一年的過去，除了我外貌的變化，陪伴著我的機車里程表也從一開始的 3000 公里超過 72000 公里，而我的心智與思維也在一點一滴的累積中成熟起來。

感謝我的指導教授：林育立教授這七年來，必須耐著性子指導我這駑鈍的學生，也感謝老師這七年來對我的照顧，讓我不會在這浩瀚如海的學術領域中，

迷失方向。您的教誨，有如指南針一般，可以讓我有著踏實的方向，不會慌張。

還有系上的助理燃珠大姊，常常幫我許多東西，讓我可以快速的把許多雜事辦完，還有無敵好人立言學弟，每每幫我處理一堆有的沒的流程，以及常常告訴我第一手資訊，讓我能夠在第一時間之內完成許多事務，真是太感謝。任貽明主任，您也是知道我能畢業時，就不會做任何瑣事，讓我有著最大的自由度。在此也要說聲感謝！還有系上許多的老師，鄭藏勝教授，吳泓瑜教授，邱奕契教授，葉明勳教授，簡錫新教授，馬廣仁教授等等系上許多教授，在我求學期間，你們也會不停的教導我，有時也會聆聽我的報怨，相當感謝！

實驗室的歲月之中，每一屆的學弟也都會幫我分擔一些事務，和勳學弟，俊宏學弟，阿冠學弟，志中學弟，小安學弟，威仁學弟，瑋倫學弟，江禹學弟，凰齊學弟，小郭學弟，信志學弟。感謝你們讓我在去工研院的時候，幫我處理一些學校的事務，讓我可以全心全意的進行實驗。當然另外還有其他實驗室的學弟

們，猴老大學弟，書偉學弟等等…（太多寫不完），也謝謝你們的幫忙，讓我有

著許多便利。在此，祝福你們，畢業的人找到好工作，還再為學術努力的，則可以順利畢業。

此外，許多畢業的學長姊們，啟弘學長，順子學長，右斌學長，小光學長，

瑜鎂學姐，阿山學長，奇彰學長也會幫我注意現在社會的動向，讓我不會與社會脫節太多，也謝謝你們常常帶我參與聚會，讓我在新竹的生活更多采多姿。大學同學們的鼓勵，也是我支柱之一，信彥，阿康，阿展，小丸子，力誠，蛋頭，大姊，耀祥，也祝你們有美好的工作與前途。在碩士班所認識的好伙伴，首先謝謝阿良也是經常被我找去打球和無緣無故被我打擾，祝你婚姻美滿唷！豪氣的偉菘祝你公司越開越大，還有志曄謝謝你，三不五時的跟我打屁，放鬆我的緊張的氣

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息。而在中正念博士的飛官，我也祝你快快畢業，快點升將軍。而遠在美國那方號稱鍍膜雙雄之一的仁泰，也謝謝你，常常要你在你的深夜，我的白天聽我抱怨，

感恩拉～還有不可以忘記的陳玉珍小姐，謝謝妳這數年來的陪伴，讓我能夠有安穩的感覺。

在新竹十一年求學期間，零零總總的認識不少家庭與人們。蔡媽媽，在此恭喜妳開店了，逢年過節常常去妳家叨擾真不好意思，而蔡伯伯的非凡手藝更是讓我記憶尤深。還有每次出國都會麻煩的 KELLY，真感謝拉。因為有妳的幫忙，

所以我出國時候才可以放心許多。遠在芝加哥的郭伯伯，謝謝你在我去美國出席國際會議的時候常常照顧我，使我不會有慌亂的情況。還有大學城美食街的老闆們，謝謝你們都會給我比較大份的餐點，讓我獲得充分的營養好讓我良好的體力，繼續往學術之路奮鬥及打拼。另外，榮志車行的黃老闆，謝謝你的巧手讓我的機車總是能保持最佳狀態，使我在往返學校與工研院的路途之間，可以有著安全且安心的交通工具，應付突發的任何狀況。NOVA 裡面的李小胖，小楊，阿偉，

謝謝你們給我對於 3C 電子產品的幫助與協助，如果沒有你們幫我救回我的硬碟的資料，我想我現在應該不知在哪敲鍵盤吧！

而在工研院的日子裡，首先感謝李文錦博士的大力幫忙與解惑，使得我在電化學的部分能有所增長，也謝謝您不辭辛勞的教導以及常常幫我收拾許多我掉東掉西的紕漏。而平日的生活交談中，更教導了我許多的做人做事道理，還有必須忍耐我這個從零開始的工讀生，真是萬分感謝。而我們的組的領導人賴宏仁副組長，也十分感謝您對我的照顧，每每跳出來挺我。陳興華主任，謝謝你讓我能夠自由的使用實驗室的儀器，這對我來說可是相當大的幫助，也就是這種機會，讓我能夠順利畢業。材化所 J400 實驗室裡面的各位伙伴，王正全博士，李秉章博士，明偉，雅靜，國偉，靜宜，希平，豪哥，彥倫，佳瑩。謝謝你們不會因為我是工讀生，而對我有所保留，你們也會將許多知識傳授給我，也學到許多事務，還有每次有好料的都一定為我保留一份以及找我，真是非常感謝。去異鄉求學的君怡，忻甜，我在這也祝福妳們能夠有順利的求學之路，與充實的異鄉生活。而帶領我進入超電容領域的陳冠良先生，在此我也要謝謝你，因為你的帶領讓我有機會能夠一窺超電容之奧妙，也祝福你有更好的工作環境。

此外，材化所的籃球隊員們：肇英,俊璋,盈志,昇峰,青城.聖文,宏仲,阿閔, 昭仁,正軒。謝謝你們讓我有參與你們行列的機會，讓我在工研院的生活除了在嚴緊的學術研究壓力之外，也有其他輕鬆的休閒運動機會。而在工研院球場打球除了讓我認識了更多的人們，也使我有良好的體能讓我可以順利完成研究。還有球場上許多不知名的伙伴，謝謝你們傳授了我許多球場的技巧與經驗。

最後感謝我的家人，黃漢炎先生，林杏女士，黃舶滄先生，有了你們的不間斷的支持與鼓勵，我才能完成這博士學位。在攻讀博士班的旅程中，你們的辛勞是種無形的壓力，如今你們終於可以不必再為我這個兒子操煩了。在此，為你們獻上我最深的感謝與祝福。

西元二零零九年十月黃厚升於台灣新竹中華大學鍍膜技術實驗室筆

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Chief Contents

Abstract……….………...……….….…...….…... Ⅰ Acknowledgement………...………...………….………Ⅱ

Chief Contents………..Ⅳ

Content of Tables………..……….………...…Ⅷ Contents of Figures……….………...…….. ………Ⅹ

Chapter 1 Introduction……….………...……..1

1-1 Foreword……….………..1

1-2 Motivation and Background……….2

Chapter 2 Literature Survey……….…….………..4

2-1 Supercapacitor………...4

2-2 The Developing History of Supercapacitor………..5

2-3 The Application of Supercapacitor………...7

2-4 Type of Supercapacitor………...8

2-4-1 Double-Layer Capacitor………8

2-4-2 Pseudo-Capacitor………...9

2-5 The Preparation of Metal Oxide Electrode……….10

2-5-1 Thermal Decomposition Method……….11

2-5-2 Sol-Gel Process………11

2-5-3 Cyclic Voltammetric Deposition……….……….12

2-5-4 Anodizing………13

2-5-5 Cathodic Deposition………..…..14

2-6 Carbon Nanotube………14

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2-6-1 Structure of Carbon Nanotube and its Electrical Characterization…...15

2-6-2 Storage Energy by Carbon Nanotube………...…………..……….17

2-6-3 Electrochemistry of Carbon Nanotube………..………..17

2-6-4 Supercapacitor of Carbon Nanotube………..………..18

2-6-4-1 The Supercapacitor Electrode Mixed the Polymer with Carbon Nanotube……….……...…..18

2-6-4-2 The Supercapacitor Electrode Mixed the Ruthenium with Carbon Nanotube………..18

2-6-4-3 The Supercapacitor Electrode Manufactured by Other Processes of Carbon Nanotube…………...………...19

2-7 Purification of Carbon Nanotube………..………..20

2-7-1 Oxidation Method………20

2-7-2 SDS Suspension Filtered Method………20

2-7-3 Chromatography………..21

Chapter 3 Experimental Processes………...……….………...35

3-1 Pre-treatment of Substrate………...35

3-2 Deposition Solution………36

3-3 Cathodic Deposition………38

3-4 Analytical Method………..38

3-4-1 The Characteristic of Coating by Various Instruments………38

3-4-2 Analysis Electrochemical Characteristic……….40

Chapter 4 Results and Discussion………...………...…...53

4-1 The Effect of Deposition Conditions on Capacitance……….……53

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4-1-1-1 Effect of Capacitance of Hydrous Ruthenium Oxide by Anodic

Oxidization………...55

4-1-1-2 The Effect of Thermal Treatment on Capacitance of Hydrous Ruthenium Oxide Coating………..……….…..………...56

4-1-2 Carbon Nanotube Added into the Deposition Processes………..……...…59

4-1-3 Dispersed Carbon Nanotube Added into the Deposition Processes…....…64

4-2 Analysis the Structure of Coating Layer……….…67

4-2-1 TEM Investigation……….…..67

4-2-2 Polarization Curve Investigation………...…..70

4-2-3 The Percentage of Double Layer Capacitor………...…..71

4-3 Subsequent Treatment……….72

4-3-1 TGA Thermal Treatment……….72

4-3-1-1 Microstructure Investigation After Heat Treatment……….74

4-3-2 Test in Charge/Discharge……….75

4-3-2-1 The Effect of Capacitance from the Charge/Discharge Cycles……...75

4-3-2-2 The Structure of the Specimens Experienced 10⁵ Charge/Discharge Cycles………...76

4-3-2-3 The Percentage of Double Layer Capacitor of the Specimen after 10⁵ Charge/Discharge……….77

4-3-3 XPS Investigation…….………...…78

4-3-4 XRD Investigation………...80

4-3-4-1 XRD of Basic Solution and with Anodic Oxidization and 200℃ Heat Treatment………..…80

4-3-4-2 The Effect of Specimen With or Without Carbon Nanotube Additive and After 550℃ Thermal Treatment………...…...…80 4-3-4-3 The Specimen With or Without Carbon Nanotube Additive at Various

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Deposition Periods With 500℃ Thermal Treatment………..………..81 4-3-4-4 The Specimen With or Without Carbon Nanotube Additive under 10⁵

Charge/Discharge Cycles……….…81

Chapter 5 Conclusion………..……….…...…………..167

Chapter 6 References………....…...171

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Content of Table

【Table 2-1】 The difference of electrochemical capacitor, traditional capacitor, and battery………….………..………..……...…….23

【Table 2-2】 The market and technical bottlenecks of supercapacitor……...24

【Table 2-3】 The development of embedded device..………...25

【Table 2-4】 The advantages and disadvantages of preparing the metal oxide supercapacitor electrode………..……..……26

【Table 2-5】 The various methods to purify carbon nanotube………27

【Table 3-1】 The specification of carbon nanotube additive in this study...46

【Table 4-1】 The effect of 0.5 ASD anodic oxidization for the specimen with or without 20% ethanol additive (F/g)………..………..83

【Table 4-2】 The effect of 0.5 ASD anodic oxidization for the specimen with or without 20% ethanol additive (F/cm²)………...….83

【Table 4-3】 The effect of 0.5 ASD anodic oxidization for the specimen with or without 0.02M surface-active agent additive (F/g)…………....83

【Table 4-4】 The effect of 0.5 ASD anodic oxidization for the specimen with or without 0.02M surface-active agent additive (F/cm²)…………83

【Table 4-5】 The effect of current density of anodic oxidization for capacitance (F/g)…………...……….………..83

【Table 4-6】 The effect of current density of anodic oxidization for capacitance

(F/cm²)……..………...……83

【Table 4-7】 The effect of thermal treatment for capacitance (F/g)………….84

【Table 4-8】 The effect of thermal treatment for capacitance (F/cm²)……….84

【Table 4-9】 The capacitance of specimens with various percentage carbon nanotube additive at various deposition periods (F/g)…....…..84

【Table 4-10】 The capacitance of specimens with various percentage dispersing

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carbon nanotube additive at various deposition periods (F/g)...84

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Content of Figures

【Figure 2-1】 The difference of battery, supercapacitor, and capacitor...….……….….31

【Figure 2-2】 SupercapacitorⅠ……..………...…….…31

【Figure 2-3】 SupercapacitorⅡ………..……….………32

【Figure 2-4】 Supercapacitor bus………32

【Figure 2-5】 The double layer diagram…………...………..33

【Figure 2-6】 The various structures of carbon……….………..33

【Figure 2-7】 The various structures carbon nanotube by the rolling flat graphite…...34

【Figure 2-8】 Carbon nanotube in armchair structure and chiral structure...34

【Figure 3-1】 The experimental processes……….……47

【Figure 3-2】 The microstructures of Ti substrate after chemical etching. (a) the after 5 wt% HF, (b) the detailed etching after 50 wt% HCl at 90℃…………..48

【Figure 3-3】 The nanostructure of carbon nanotube additive in this study...……….48

【Figure 3-4】 The schematic diagram of cathodic deposition………49

【Figure 3-5】 The schematic diagram of CV scanning………...………...49

【Figure 3-6】 The theoretical CV curve……….50

【Figure 3-7】 The real CV curve……….…..50

【Figure 3-8】 The polarization curve………51

【Figure 3-9】 The curve of distinction of double layer capacitor.………..52

【Figure 4-1】 The electrical capacity characteristics of specimen with ethanol and surface-active agent additive at 1.5 pH and the capacitance is 428 F/g and 0.238 F/cm²………...………...85

【Figure 4-2】 The difference of electrical capacity characteristics of specimens of the electrolyte were with or without ethanol additive. Solid line: the CV curve of electrode A is electrolyte with ethanol additive, the capacitance is 428 F/g and 0.238 F/cm². Dotted line: The CV curve of electrode B which is electrolyte without ethanol additive, the capacitance is 255 F/g and 0.107 F/cm²……….………..………86

【Figure 4-3】 The difference of electrical capacity characteristics of specimens of the electrolyte were with or without ethanol additive and after anodic

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treatment in 0.5 ASD. Solid line: the CV curve of electrode A after anodic treatment in 0.5 ASD, the capacitance is 381 F/g and 0.234 F/cm². Dotted line: The CV curve of electrode B after anodic treatment in 0.5 ASD, the capacitance is 232 F/g and 0.123 F/cm²………..…..…..……87

【Figure 4-4】 The difference of electrical capacity characteristics of specimens of the electrolyte were with or without surface-active agent additive. Solid line:

the CV curve of electrode C is electrolyte with surface-active agent additive, the capacitance is 343 F/g and 0.312 F/cm². Dotted line: The CV curve of electrode D which is electrolyte without surface-active agent additive, the capacitance is 428F/g and 0.237

F/cm²……….………..88

【Figure 4-5】 The difference of electrical capacity characteristics of specimens of the electrolyte were with or without surface-active agent additive and after anodic treatment in 0.5 ASD. Solid line: the CV curve of electrode C after anodic treatment in 0.5 ASD, the capacitance is 381 F/g and 0.233 F/cm². Dotted line: The CV curve of electrode D after anodic treatment in 0.5 ASD, the capacitance is 327 F/g and 0.322 F/cm²……….89

【Figure 4-6】 The difference of electrical capacity characteristics of specimens of the electrolyte were in the value of pH. Solid line: the CV curve of electrode E is electrolyte in pH: 1.5 the capacitance is 334 F/g and 0.261 F/cm². Dotted line: The CV curve of electrode F is electrolyte in pH: 1.0, the capacitance is 165 F/g and 0.084 F/cm²………..….…..90

【Figure 4-7】 The microstructure of hydrous ruthenium oxide………..…91

【Figure 4-8】 The microstructure of hydrous ruthenium oxide after 0.5 ASD anodic oxidization………..91

【Figure 4-9】 The microstructure of hydrous ruthenium oxide after 1 ASD anodic oxidization………..…91

【Figure 4-10】 The microstructure of hydrous ruthenium oxide after 1.5 ASD anodic oxidization………..…91

【Figure 4-11】 The difference of electrical capacity characteristics of specimens were before and after 0.5 ASD anodic oxidization. Solid line: before 0.5 ASD (5^th), the capacitance is 390.850 F/g and 0.210 F/cm². Dotted line: after

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【Figure 4-12】 The difference of electrical capacity characteristics of specimens were before and after 1.0 ASD anodic oxidization. Solid line: before 1.0 ASD (5^th), the capacitance is 353 F/g and 0.184 F/cm². Dotted line: after 1.0 ASD (5^th), the capacitance is 353 F/g and 0.135 F/cm²..………...93

【Figure 4-13】 The difference of electrical capacity characteristics of specimens were before and after 1.5 ASD anodic oxidization. Solid line: before 1.5 ASD (5^th), the capacitance is 367.490 F/g and 0.163 F/cm². Dotted line: after 1.5 ASD (5^th), the capacitance is 345.821 F/g and 0.120 F/cm².…...94

【Figure 4-14】 The difference of electrical capacity characteristics of specimens after different current of anodic oxidization.……...…...………..95

【Figure 4-15】 The declined percentage of measured capacitance value VS different anodic oxidization current (F/g).………….……….96

【Figure 4-16】 The declined percentage of measured capacitance value VS different anodic oxidization current (F/cm²).……….…...96

【Figure 4-17】 The microstructure of hydrous ruthenium oxide after 50℃ thermal treatment was observed.(a)1500x, (b)5000x…..………..…..97

【Figure 4-18】 The microstructure of hydrous ruthenium oxide after 100℃ thermal treatment was observed.(a)1500x, (b)5000x…..………..…..97

【Figure 4-19】 The microstructure of hydrous ruthenium oxide after 150℃ thermal treatment was observed.(a)1500x, (b)5000x…..………...…..97

【Figure 4-20】 The microstructure of hydrous ruthenium oxide after 200℃ thermal treatment was observed.(a)1500x, (b)5000x…..………..………....…..98

【Figure 4-21】 The microstructure of hydrous ruthenium oxide after 250℃ thermal treatment was observed.(a)1500x, (b)5000x…..………....………..…..98

【Figure 4-22】 The microstructure of hydrous ruthenium oxide after 300℃ thermal treatment was observed.(a)1500x, (b)5000x…..………....………..…..98

【Figure 4-23】 The difference of electrical capacity characteristics of specimens were before and after 50℃ thermal treatment. Solid line: before after 50℃

thermal treatment (5^th), the capacitance is 354 F/g and 0.273 F/cm². Dotted line: after 50℃ thermal treatment (5^th), the capacitance is 274.050 F/g and 0.218 F/cm²……….…..…..99

【Figure 4-24】 The difference of electrical capacity characteristics of specimens were

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before and after 100℃ thermal treatment. Solid line: before after 100℃

thermal treatment (5^th), the capacitance is 344 F/g and 0.254 F/cm². Dotted line: after 100℃ thermal treatment (5^th), the capacitance is 216.600 F/g and 0.164 F/cm²………...100

thermal treatment (5^th), the capacitance is 340 F/g and 0.260 F/cm². Dotted line: after 150℃ thermal treatment (5^th), the capacitance is 174 F/g and 0.114 F/cm²………..………….101

thermal treatment (5^th), the capacitance is 361.270 F/g and 0.261 F/cm². Dotted line: after 200℃ thermal treatment (5^th), the capacitance is 241.620 F/g and 0.179 F/cm²………...…..102

thermal treatment (5^th), the capacitance is346.770 F/g and 0.253 F/cm². Dotted line: after 250℃ thermal treatment (5^th), the capacitance is 224.400 F/g and 0.173 F/cm².……….103

thermal treatment (5^th), the capacitance is 346.100 F/g and 0.265 F/cm². Dotted line: after 300℃ thermal treatment (5^th), the capacitance is 70.080 F/g and 0.096 F/cm².……….……104

【Figure 4-29】 The difference of electrical capacity characteristics of specimens VS various thermal treatment.………105

【Figure 4-30】 The declined percentage of measured capacitance value VS different thermal treatment (F/g).………....106

【Figure 4-31】 The declined percentage of measured capacitance value VS different thermal treatment (F/cm²).………....106

【Figure 4-32】 The difference of electrical capacity characteristics of specimens with

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0.05wt% carbon nanotube added at various deposition time………….107

【Figure 4-33】 The difference of electrical capacity characteristics of specimens with 0.1wt% carbon nanotube added at various deposition time…………...108

【Figure 4-34】 The difference of electrical capacity characteristics of specimens with 0.25wt% carbon nanotube added at various deposition time………….109

【Figure 4-35】 The capacitance of specimens with various percentage carbon nanotube added VS deposition time………...…110

【Figure 4-36】 The difference of electrical capacity characteristics of specimens at 5 minutes deposition time with various percentage carbon nanotube added………...111

【Figure 4-37】 The difference of electrical capacity characteristics of specimens at 10 minutes deposition time with various percentage carbon nanotube added…...……….112

【Figure 4-38】 The difference of electrical capacity characteristics of specimens at 15 minutes deposition time with various percentage carbon nanotube added……….…..113

【Figure 4-39】 The difference of electrical capacity characteristics of specimens at 30 minutes deposition time with various percentage carbon nanotube added………...114

【Figure 4-40】 The difference of electrical capacity characteristics of specimens at 60 minutes deposition time with various percentage carbon nanotube added……….…..115

【Figure 4-41】 The capacitance of specimens at various deposition time VS concentration of carbon nanotube added………..116

【Figure 4-42】 The microstructure of hydrous ruthenium oxide specimens with 0.05wt%

carbon nanotube additive at various deposition periods.………....117

【Figure 4-43】 The microstructure of hydrous ruthenium oxide coating added with 0.1wt% carbon nanotube at various deposition periods……...118

【Figure 4-44】 The microstructure of hydrous ruthenium oxide coating added with 0.25wt% carbon nanotube at various deposition periods………...119

【Figure 4-45】 The difference of electrical capacity characteristics of specimens with dispersing 0.0125wt% carbon nanotube added at various deposition

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time………..120

【Figure 4-46】 The difference of electrical capacity characteristics of specimens with dispersing 0.025wt% carbon nanotube added at various deposition time.……….…121

【Figure 4-47】 The difference of electrical capacity characteristics of specimens with dispersing 0.05wt% carbon nanotube added at various deposition time………..122

【Figure 4-48】 The difference of electrical capacity characteristics of specimens with dispersing 0.1wt% carbon nanotube added at various deposition time………..123

【Figure 4-49】 The capacitance of specimens with various dispersing carbon nanotube added VS deposition time………...124

【Figure 4-50】 The difference of electrical capacity characteristics of specimens at 5 minutes deposition time with various dispersing percentage carbon nanotube added………...…125

【Figure 4-51】 The difference of electrical capacity characteristics of specimens at 10 minutes deposition time with various dispersing percentage carbon nanotube added………...126

【Figure 4-54】 The difference of electrical capacity characteristics of specimens at 60 minutes deposition time with various dispersing percentage carbon nanotube added………..129

【Figure 4-55】 The capacitance of specimens at various deposition time VS concentration of dispersing carbon nanotube added………..…130

【Figure 4-56】 The microstructure of hydrous ruthenium oxide coating added with 0.0125wt% dispersing carbon nanotube at various deposition periods………131

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【Figure 4-57】 The microstructure of hydrous ruthenium oxide coating added with 0.025wt% dispersing carbon nanotube at various deposition periods...132

【Figure 4-58】 The microstructure of hydrous ruthenium oxide coating added with 0.05wt% dispersing carbon nanotube at various deposition periods...133

【Figure 4-59】 The microstructure of hydrous ruthenium oxide coating added with 0.1wt% dispersing carbon nanotube at various deposition periods….134

【Figure 4-60】 The atomic structure of RuOx(OH)y………..135

【Figure 4-61】 The high-resolution TEM image of the specimen was without carbon nanotube additive which RuO2 microstructure was observed in (2 1 0), (2 1 1) and zone axis [0 0 1].………..………..136

【Figure 4-62】 The high-resolution TEM image of the specimen with 0.05 wt% dispersing carbon nanotube additive at 5 minutes deposition period which RuO2

microstructure was observed in (2 1 0) and zone axis [0 0 1], and Ru crystal in zone axis [0 0 0 2]………...…..….137

【Figure 4-63】 The high-resolution TEM image of specimen with 0.05 wt% dispersing carbon nanotube additive at 10 minutes deposition period which RuO2

microstructure was observed in zone axis [0 0 1], and observed the Ru crystal in (0 0 0 2).………...………....138

【Figure 4-64】 The high-resolution TEM image of specimen with 0.05 wt% dispersing carbon nanotube additive at 15 minutes deposition period, which RuO2

microstructure was observed in (2 1 0) and zone axis [ī 2 1].………..139

microstructure was observed in (2 1 0) and zone axis [0 0 1].…………140

microstructure was observed in (2 1 0) and zone axis [0 0 1].………..141

【Figure 4-67】 The difference of polarization curves were the electrolytes of without carbon nanotube additive, with carbon nanotube additive, and with dispersing carbon nanotube additive. …...……….……..142

【Figure 4-68】 The distinguishable double-layer capacitance of specimen was without

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carbon nanotube additive..………..……….143

【Figure 4-69】 The distinguishable double-layer capacitance of specimen was with carbon nanotube additive……….………….……..………143

【Figure 4-70】 The TGA measurements of different specimens which were (a) without carbon nanotube additive (b) dispersed carbon nanotube additive at 5 minutes deposition period (c) dispersed carbon nanotube additive at 10 minutes deposition period (d) dispersed carbon nanotube additive at 15 minutes deposition period (e) dispersed carbon nanotube additive at 30 minutes deposition period (f) dispersed carbon nanotube additive at 60 minutes deposition period.………...144

【Figure 4-71】 The difference of TGA of specimens with various deposition

concentrations………...145

【Figure 4-72】 The declined capacitance percentage of specimens VS various thermal temperatures………146

【Figure 4-73】 The high-resolution TEM image of specimen without added carbon nanotube at 550℃ thermal treatment which is the RuO2 particle with zone axis [

ī

1 0], (2 0 0), and (1 1 1)……….147

【Figure 4-74】 The high-resolution TEM image of specimen with 0.05 wt% dispersing carbon nanotube additive at 5 minutes deposition period and 550℃

thermal treatment which RuO2 microstructure was observed in zone axis [ī 1 0], and Ru crystal (1 0 ī 1)...148

thermal treatment which RuO2 microstructure was observed in (1 1 1) zone axis [ī 1 0], and Ru crystal with zone axis [1 0 ī 1]...………149

thermal treatment which Ru crystal was observed in (1 0 ī 0)..………150

thermal treatment which RuO2 microstructure was observed in (1 0 1)

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zone axis [1 0 1], and Ru crystal with (1 0 ī 0), (1 0 ī 1)...………151

thermal treatment which Ru crystal was observed in (1 0 ī 0).………152

【Figure 4-79】 The capacitance change of specimens VS charge/discharge cycles

(F/cm²)………...153

【Figure 4-80】 The declined capacitance percentage of specimens VS charge/discharge cycles……….………….154

【Figure 4-81】 The microstructure of hydrous ruthenium oxide with and without added carbon nanotube which with and without experienced charge/discharge

10⁵ times………..……….…….155

【Figure 4-82】 The high-resolution TEM images of specimen without carbon nanotube additive and after charge/discharge 10⁵ times, which RuO2 microstructure was observed in (2 1 1) zone axis [ī 1 0], and Ru crystal in (1 0 ī 1).….156

【Figure 4-83】 The high-resolution TEM images of specimen with 0.05 wt% dispersing carbon nanotube additive and after charge/discharge 10⁵ times which RuO2 microstructure was observed in (1 1 1) , and Ru crystal was observed in (1 0 ī 0) and zone axis [0 0 0 2].……….………..……..…157

【Figure 4-84】 The distinguishable double-layer capacitance of specimen without added carbon nanotube with charge/discharge 10⁵ times.……….……158

【Figure 4-85】 The distinguishable double-layer capacitance of specimen added carbon nanotube with charge/discharge 10⁵ times.………....…158

【Figure 4-86】 The XPS of specimen without carbon nanotube additive……….…….159

【Figure 4-87】 The XPS of specimen without carbon nanotube additive at 300℃ thermal treatment……….………..…..160

【Figure 4-88】 The XPS of specimen without carbon nanotube additive at 550℃ thermal treatment……….……161

【Figure 4-89】 The XPS of specimen without carbon nanotube additive after 10⁵

charge/discharge cycles.……….162

【Figure 4-90】 The difference of XRD of specimens without carbon nanotube additive and with 0.5 ASD anodic oxidization and at 200℃ thermal treatment….…163

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【Figure 4-91】 The difference of XRD of specimens with and without carbon nanotube additive and with and without 550℃ thermal treatment…………...…164

【Figure 4-92】 The difference of XRD of specimens with and without 0.05 wt% dispersed carbon nanotube additive at various deposition periods and 550 ℃ thermal treatment………165

【Figure 4-93】 The difference of XRD of specimens with and without 0.05 wt% dispersed carbon nanotube additive and with and without charge/discharge 10⁵ cycles.………….………....166

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Chapter 1 Introduction

1-1 Foreword

Most of electricity loadings of electrical appliances were changed with different operating stages. For example, the electrical appliances need greater powers at the starting-up stage. However, suddenly higher current could not only cause damages to electrical appliances, but even the risk of fire caused by electrical wires burning.

Therefore, additional energy storage device that provides quick high-density power to replace the main power supply is needed.

The rechargeable battery sets used for many electronic products have the same problem during charging and discharging cycles. In the rechargeable battery sets, it often combines several lithium-ion batteries. However, charge-discharge behavior between two lithium-ion batteries will be different even in a most precise design. One battery is full-recharged in a rechargeable battery set, the others could be over-charged. These over-loading or over-resting processes would accelerate the aging process of batteries. After several times of charging and discharging, the difference of batteries would be sharply enlarged and the function of battery set function will be limited by the worst one in the batteries set.

The rechargeable battery sets used for many electronic products have the same problem during charging and discharging cycles. In the rechargeable battery sets, it often combines several lithium-ion batteries. However, charge-discharge behavior between two lithium-ion batteries will be different even in a most precise design. One battery is full-recharged in a rechargeable battery set, the others could be over-charged. These over-loading or over-resting processes would accelerate the aging process of batteries. After several times of charging and discharging, the

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difference of batteries would be sharply enlarged and the function of battery set function will be limited by the worst one in the batteries set.

Therefore, if average power storage device can be used to combine with the rechargeable battery, those could solve above problem. Distribute the battery power equally to each cell, which over-loading, over-resting can be avoided and can increase the life of battery. When the charging moment, the design of equalization do not only used in working batteries, but also adjusts the batteries continually to make each cell has the same electric efficacy. Therefore this study was focused on the supercapacitors what can share power effect and extend the life of electrical appliance.

The purpose of this study will focus on supercapacitor which can not only provide large capacitance, but also have the function of equalization between battery cells.

1-2 Motivation and Background

The idea of this study was created by new generation green energy vehicles of using electric battery. Besides, the supercapacitors have the advantages of lighter, thinner, shorter, and smaller compare to existed car battery.

Cathode deposition method was utilized in this study to prepare the ruthenium oxide-carbon nano tubes. Since cathode deposition method was easier control. At the same time, to control the coating structure and electrical characterization changing potential/current was charged.

Carbon nanotubes have advantage of high surface area and high conductivity, which can provide the effect of electric double-layer capacitance. So this study was used the hydroxide ruthenium oxides mixed with carbon nanotubes to taken the both of their advantages, which developed the better electrode capacitance. In order to

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increase the surface area and the practicality of component effectively, this study combined carbon nanotubes with the electroplating technology expected to the outstanding characteristics of carbon nanotubes that effectively promoted the status of quality of the supercapacitance components.

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Chapter 2 Literature Survey

2-1 Supercapacitor

Supercapacitor or electrochemical capacitor is a kind of power storage between rechargeable battery and traditional capacitor. Supercapacitor does have higher power density and much charge-discharge cycle numbers which was compared with the rechargeable battery. And compared with traditional capacitor, it has larger energy density. Besides, it has many advantages as un-maintenance, high reliability, high instant electricity power, and small size. The surface characteristic of supercapacitor electrode does supply energy density of several to tens thousands of times of traditional capacitors, and supercapacitor has much cycle numbers except with high power density characteristic. Supercapacitor is a new type device, which has both characteristics of traditional capacitor and battery. It causes widespread attention and substantial use recently.

Although the energy density of electrochemical capacitor does not as powerful as battery, it has high power density. To use for power supply, the supercapacitor can be used mixed with battery. This hybrid power system not only use the high energy density of batteries for using in the long-term, but also provide the stable voltage and required pulse current from the high power density electrochemical capacitor. The stable voltage function of charging system will only required when the pulse current is needed. In this way, the battery can supply the current to the circuit system, and part of currents would also supply to the capacitor. The capacitor can provide the pulse current to the loading required current. Hybrid power system was designed in combining the capacitor and the battery which could reduce the cost and extend the battery life as shows in Fig 2-1 [1-4].

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2-2 The Developing History of Supercapacitor

In 1887, German physicists Helmholz and Perrin forward “Double-Layer” type of flatting capacitor model [152]. When Helmholz did the study on solid/liquid interface, and found when the metal plate or other conductor did inserted the electrolyte solution, the coulomb electrostatic, Van Der Waals force, and covalent forces did arise the stable double layer charge on the metal surface that is mean the Double-Layer Structure. This structure has compact structure that similar to the flatting capacitor.

And this is a simple model, which only applied in the stronger electrolyte concentration case. In fact, the structure of double layer capacitors does not as compact as Helmholz’s assertion.

1913, Gouy and Chapman proposed the “distributing double layer” model. That model considered the affect of thermal transfer of atoms. The law of distribute atoms in the space of potential energy was scattered of in the contiguous interface layer, and then produced the electrical “distributing layer”. 1924, Stern [13] combined the reasonability part of the above two models to set up of the Gouy-Chapman-Stern model (GCS model for short). The principle of double layer capacitors had been made in 1887, but the researches were been developed in the 60’s of 20th century. 1954, the United States company GE successfully produced the low-voltage and large-capacity double layer capacitor. 1965, North American company Rock Well developed the solid electric double layer capacitor. The end of 60's to the early 70’s in the 20th century, the United States had large number of researches and results in the liquid double layer capacitor that was created the work voltage 8V and 0.2F double layer capacitors in computers successfully [5, 13].

The earliest electrochemical capacitor product was made by Panasonic Company in

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1978 and named as the Gold Capacitor, which had 1.6V, 10F [6]. In 1980, NEC produced successfully the 0.5F supercapacitor and brought it into the spare device power market of the electronic data storage system components successfully [7]. In the early 80’s of 20th century, Panasonic Electric Company introduced the products with 5.5V, 0.1-0.3F [6].

Since 1990, the researches and developments of double layer capacitor were progressed fiercely. Several companies in United States and Japan had released the electric double-layer capacitors which had tens operating voltage with thousands micro-Faraday, as shown in Figure 2-2 and 2-3. Afterward, in order to further enhance the capacity, the “Faraday Capacitor” was been developed and named “Pseudo Capacitor”. The distributed redox active matter on the high specific surface substrate was used in this capacitor, and further maximize the Faraday capacitance and the bottom surface of substrate will also provide the double layer capacitance.

An example of material used as pseudo-capacitance will be ruthenium oxide. The capacity from ruthenium oxide production was more 10 times than carbon made, this is the reason of the reaction between ruthenium ion (Ru²⁺, Ru³⁺, and Ru⁴⁺) and H⁺ ions which caused the Faraday current on the electrode surface. Zheng [8, 9]was used the amorphous RuO²‧xH2O electrode that capacity can supplied 720 F/g. Therefore, RuO2 became very attractive electrode materials for electrochemical capacitors.

Miller [10, 11] did deposited nanometer ruthenium particle on the carbon gel, which had 206 F/g capacity when the 35% ruthenium was deposited on the surface. Lin [12]

also made the composite electrode from carbon gel and combined with ruthenium, which with 197 F/g capacitance at the 13.3wt% of ruthenium on the surface.

Although the supercapacitor products were been appeared latter, it has many advantages compared with other energy storage devices as shown in Table 2-1. The

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small-sized personal electrical appliance and large-sized infrastructure. However, there were many technical bottlenecks need to be solved, that is why the electrochemical capacitor can not be as popular as other energy storage devices. The application and technical bottlenecks are shown in Table 2-2 for detailed description.

2-3 The Application of Supercapacitor

The initial utilization of supercapacitor was used in the spare power of electrical storage and the connection with battery. Since the 90's of 20th century, personal computers, communications equipment, and various kinds of power products were used wildly which provide a huge market for the supercapacitors [13, 14].

Since high performance electronic products and wireless communications become better and better, the IC production were not only being the higher level technology developed, but also IC packaging should be satisfied for the needs of IC development continually. Also since high-speed and high frequency signal transmission shortens the distance, the need of passive and active devices is increased rapidly. According to the report from Motorola [15], the using of the circuit board area and the length of wire using between devices can be reduced by 40%, such as shown in Table 2-3. At the same time, it will also reduce the number of assembly devices used which can not only enhance the quality of equipment performance, but also improve the application of space. And most importantly, it will reduce the coat. Capacitors, resistors, and inductances will place into the inner layer of substrate board, to replace the traditional discrete passives devices [16]. Supercapacitor is small, more powerful, lighter, and will be utilized in the future [17-25].

Environmental protection is a very important issue for human being. The research

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and development of electric vehicle could reduce the vehicles exhaust gas. Therefore, the supercapacitor with thousands farad can not only be used in back-up power of general electronic products, but also can be used in short-time power supplied of electric vehicles. Supercapacitor can also provide the peaked horsepower of starting, accelerating and up-hilling of electric vehicles and eliminated the defects from the over-discharge of battery to increase the life of battery. Besides, the supercapacitor has very widely used in the field of aerospace, submarines and other military applications [26, 27]. The supercapacitor bus was first to use on Aug. 28. 2006. at Shanghai the metropolis of China. This application of supercapacitor is not only a major breakthrough, but also for the future life of the application of supercapacitor, as shown in Figure 2-4.

2-4 Type of Supercapacitor

The types of supercapacitor can be divided into two groups for its working principle: double layer capacitor and pseudo-capacitor. The energy density of pseudo-capacitance is 5-10 times more than double layer.

2-4-1 Double-Layer Capacitor

The double-layer supercapacitor is the storage of electrical power from the separate charges of the Coulomb's electrostatic force of between the electrode and the electrolyte, that phenomenon could be explained by the following chemical formula

［1-3］as show as Fig 2-5.

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Anode： ₋ ⁻

+

− ⇔ +

+ e

A A E

E_s ^s ［1］

Cathode： ₊

−

+ + ⇔

+ C

e E C

E_s ^s ［2］

Total ： ₊

−

− +

+ +

⇔ − +

+ C

E A A E

C E

E_s _s ^s ^s ［3］

Where Es is electrode, C⁺ is cation, and A^- is anion

However, this model can only produce the Coulomb static electricity, and can not produce the Faraday current. The carbon-supercapacitor is the representative of this type of capacitor. Activated carbon, glassy carbon, and activated carbon fiber were generally used as the substrate materials [28-33].

2-4-2 Pseudo-Capacitor

Pseudo-capacitor not only has the effect of double layer, but also has Faraday current of the charge-transfer from the surface reaction which has 5-10 times capacitance more than that in double layers. The materials using for pseudo-capacitance could be divided into two categories: (a) metal oxides: RuO2, IrO3, Co3O4, MoO3, WO3 [34], and (b) conductive polymer films, Polyaniline, Poly-pyrrole and Polythiopeene [35-39]. In these types, the RuO2 can be regarded as the typical example.

The H⁺ ion in ruthenium hydroxide RuOx．nH2O can be transferred easily into itself phase, and the Ru4⁺ from the ruthenium compounds can also work as that did, and it thereby can be greatly enhanced the capacitance. Ruthenium can have several oxidation states, which can be done redox reaction by itself, and coupled with the electric adsorption/desorption of the reversible reaction. Therefore ruthenium oxide is

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a good type of active substance for capacitors, that storage capacitance is much larger than the traditional capacitor and double-layer capacitor. The following chemical formula (1) can be used to describe the redox agencies [3, 153]：

RuOa-δ(OH)b+δ↔RuOa(OH) b+δH⁺+δe^-...（1）

Where RuOa-δ(OH)b+δ is lower oxidation state of activated hydroxide ruthenium oxides, RuOa(OH)b is higher oxidation state activated hydroxide ruthenium oxides.

Double-layer capacitor is lower a grade than Faraday capacitor. Not only the particles of activated carbon electrode were poor to contact each other, but also slowly oxidized of carbon and other reason, and caused the higher capacitor equivalent series resistance. Therefore, must to develop a new electrode material with lower resistivity and higher surface area. The best material was distributed the redox active substances onto the high surface area substrate, which the redox active substances provided Faraday capacitance and the under surface of substrate provided the double layer capacitance at the same time, thereby to increase the energy density of capacitors [5].

2-5 The Preparation of Metal Oxide Electrode

Several methods of metal oxide electrode preparation can be found in the literature as follows: Thermal Decomposition, Sol-Gel Process, Cyclic Voltammetry Deposition, Anodizing, Cathodic Deposition, Chemical Vapor Deposition, Sputtering, and Vaporization. Different methods can obtain the different types and properties of oxide electrodes. The followings described the principles and steps of metal oxide electrode preparation methods.

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2-5-1 Thermal Decomposition Method

Using the thermal treatment method, it will produce the composited materials by the decomposed precursors. There are several key elements for controlling the electrode which were the prepared oxides by the thermal decomposition and usually were the dehydrated and crystalline structures. Because the structure of oxide was too tiny and having small porous, the reaction of electron transferred only work on the electrode surface. The capacitance of electrode making by this method was found less than that for electrode with amorphous structure.

Jeong and Manthiram used the potassium dichromate (K2Cr2O7 ) mixed with hydrous ruthenium chloride (RuCl3．xH2O) in different pH and ratios environment (pH: 6.5-12), to deposit thin film by thermal decomposition method. The ratios of components that proposed were potassium: 1%, ruthenium: 73%, chromium: 27%, pH 6.5, in thermal treatment at 150℃. They found that the material has the best capacitance of 840 F/g. When the ratio of components was changed to potassium:

45%, ruthenium: 91%, chromium: 9%, pH of 12, in thermal temperature at 150℃, the capacitance was measured to be 393 F/g [40-43].

2-5-2 Sol-Gel Process

Sol-gel method was also used to produce the electrode for supercapacitor. It has dissolved the water-soluble-salt or oil-solube-alcoholate in water or organic-solvent, that will occurred the hydrolysis to produce the nano-meter particle, which was become to sol and then transform to gel by experiencing in evaporate drying. The structure, composition and coating uniformity were easily controlled during sol-gel processes. Many high purity and high uniformity materials can be easily to manufacture. However, its manufacturing process is more complex than others and

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there are many factors that should be controlled in such process. For example, the preparation of hydrous ruthenium oxides by adopting the sol-gel method was as follows: (1) mixed ruthenium tri-chloride (RuCl3) aqueous solution with potassium hydroxide (NaOH) solution and adjusted the pH to 7, that will be the ruthenium hydroxide (Ru(OH)3) precipitate formatted, (2) washed and filtered the precipitate in high temperature, and the precipitate became the ruthenium oxide powder.

Calcinations temperature was an important factor in the final crystallization of material. It was found that the maximum capacitance can be obtained when the operating temperature must below the temperature for making crystallization was used.

Zheng et al. had prepared hydrous ruthenium oxides electrode materials by this method. They prepared electrode of active material with added adhesives, which the capacitance was measured to be 720 F/g (for single electrode). Using this method, the H⁺ was very easy to transported internally and the internal Ru⁴⁺ was also reacted. It appeared that the charge and discharge cycle life of capacitor by this method has a good performance, showing the hydrous ruthenium oxides were the good candidates of material selection for the capacitors [9, 10, 44-46].

In addition, Hu et al. also used this ideal to produce the supercapacitor electrodes.

They used graphite as the electrode material, which has a very high surface area. The maximum capacitance can be as high as 1340 F/g after deducted the weight of graphite [47].

2-5-3 Cyclic Voltammetric Deposition

The cyclic voltammetry deposition method is coated material layer by layer with

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this method. The structure of producing hydrous oxide was amorphous. As compared with other methods, cyclic voltammetry not only reduce the unnecessary human error, but also control the coating thickness in accordance with the deposition conditions.

Hu with his research team were committed to the use of cyclic voltammetry method for producing the electrode of capacitors. The studied the produced oxides, growth of action, electroplating environmental. Their results showed that the hydrous ruthenium dioxide had amorphous structure and porosity surface [48] [49]. They had also prepared the manganese-nickel oxide, with contained the few amount of nickel. The capacitance of this material was reported to be 160 F/g [50]. There were several results [51-54] to produce electrode for supercapacitor using cyclic voltammetry method.

2-5-4 Anodizing

In this method, oxides were produced onto the metal surface by anodic oxidation.

In addition, a metal coating could be pre-deposited on substrate and followed by anodic oxidation treatment. The characteristics of the produced oxide were similar to that were from the cathodic deposition, the cyclic voltammetry, and the sol-gel methods.

Zhang and Tsai [55] directly deposited the manganese oxide on carbon substrate to produce the electrode material from 0.25M manganese acetate solution in the room temperature. However, it was found that the potential value of anodizing had the important impact to the material properties and electrochemical behavior of oxides.

When the electrode voltage was higher than 0.8V, the oxide porosity would be significantly reduced. The protuberant particles can be observed on the surface of electrode. Mixed of oxides with Mn³⁺ and Mn⁴⁺, can be observed when the anodic

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potential was at 0.5V. While oxide with Mn⁴⁺ was the major production when higher potential was be used.

2-5-5 Cathodic Deposition

Cathodic deposition method is also a popular method to produce the coating layer.

The advantages of this method are easy and quick. The structure of coating was usually found as hydrous with amorphous structure by this method [56-59, 111].

The crystalline structure of ruthenium dioxide had been observed by Lokhande and Park [60]. In addition, they had also explored the relationship of depositing thickness with capacitance [61]. Kuo [62] used the mixed metal solution of stibium (Sb), stannum (Sn), and ruthenium (Ru) to produce the coating solution for supercapacitor.

Vuković and Čukman used the combination of the experimental and calculated methods to analyze the theory functions and the chemical formula, based on the electrode during charge/discharge process [63]. Jang [64] used the electrophoresis to produce the ruthenium oxide electrode. Their results showed that the capacitance can be reached to 734-608 F/g. However, producing time was need for three days. This method can not produce the electrode in a short time. Table 2-4 shows the comparison of advantages and disadvantages of preparation of metal oxide electrode.

2-6 Carbon Nanotube

Since Sumio Iijima discovered carbon nanotubes in 1991, its scale and unique electrical properties attracted numerous global research teams, and has widely been adopted to use in scientific and engineering [65]. The single-walled carbon nanotube

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(SWNT) was an ideal material for the research of low dimension physics. Carbon nanotubes have many important and potential applications, such as the nano scale electronic devices, atomic force microscope probe, field emitter, and chemical sensor technology etc. [66-68].

Sensing application technology is another application for carbon nanotube although it is still in the laboratory stage. From literature, supercapacitor used of carbon nanotubes that has been reported, but the results are still very limited [5, 69-74].

2-6-1 Structure of Carbon Nanotube and its Electrical Characterization

Carbon has various structures. Graphite, carbon 60 and the carbon nanotubes are all of branches of carbon. Figure 2-6 shows (a) graphite structure, (b) diamond structure, (c) carbon 60 as football shaped, and (d) the typical carbon nanotubes.

Carbon nanotube is usually made from a 2-dimensional structure of crimping graphite. When crimped the graphite into carbon nanotube, there are three different forms of carbon nanotubes depending on the crimped method. They are single nano tubes (armchair), zigzag-type nano tubes, and chiral-type nano tubes (as Figure 2-7, 2-8). They can be expressed by

b m a n

rv= v+ v

Where, rv is the direction of curled carbon nanotubes vector, m and n are integers,

av

andbv

are the two lattice vectors of hexagonal lattice structure, θ is the angle between curly vector and a vector. The chirality and diameter of single-walled carbon nanotubes can be defined by the different (m, n) value.

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When m=0 or n=0 (θ=0ô), carbon nanotube was shows zigzag structure; and m=n or m=-2n (θ=30ô), the carbon nanotube was armchair structure; and m, n values of non-status (0ô<θ<30ô), carbon nanotube was chiral structure.

Carbon nanotube was different from nano wire which has the general characteristics of semiconductor. According to the size and spiral, single-walled carbon nanotube has various electrical characteristics, which were metal, semimetallic, and semiconductor properties. The carbon nanotube with armchair structure shows metallic characteristics, and has the finite density of states at Fermi level. When m-n ≠ 3 × integers, its electrical characteristics became to semiconductor, and the primary energy gaps Eg with diameter d was inversely proportional as to diameter. When m-n

= 3 × integer, then the electrical properties shows semimetallic characteristics and the primary energy gaps Eg=0. At this moment, the carbon nanotube curvature leaded the interaction of nonparallel PΠ orbit and NΠ orbit, and produced a small primary energy gap (that is, Eg>0) [75, 76]. It was very clearly, the smaller the radius of the single-walled carbon nanotubes, the electrical properties will be more away from becoming semi-metallic and semiconductor properties. The rehybridizarion effects of this orbit in the same m/n ratio, the primary energy gaps Eg and the diameter d were in inversely proportion, that was to Eg~1/d² [77, 78].

Carbon nanotubes usually had very good plasticity having different shape, which was affected the electrical characteristics. It was difficult to control the geometric synthesis of carbon nanotubes during the process in the past. It was also difficult to isolate the crystalline carbon nanotubes from the sub-products of reaction. However it has found recently that the size and shape of carbon nanotubes can be controlled by growing the triangular shape of single-walled carbon nanotubes in the porous anodic alumina template matrix using electrochemical oxidation method. The radius of

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of electrical conduction properties with lattice structure of carbon nanotube was executed by both simulated and experiment in many studies [5, 80, and 224].

2-6-2 Storage Energy by Carbon Nanotube

Carbon nanotube can be used as a material for energy storage device. Matsumoto et al. produced a fuel cell that used Mo2C to mix with carbon nanotubes as cathode and platinum mixed with carbon black as anode [81]. It was found that the electrode when carbon nanotube was used is better than that when other metal materials were used [82]. When carbon nanotube mixed with metal that had catalyst properties for the electrode of full-cell electrode, the performance was found better than the general carbon electrodes [83, 84]. Besides, it can be also found in the literature that the energy density of supercapacitor was produced with carbon nanotube larger than 8000 W/g [85]. The single-walled carbon nanotubes was reported to have high electric capacity of 400~650 mAh/g [86]. The electrical capacity can be raised up to 1000 mAh/g when carbon nanotube was made by ball-milling process [87].

2-6-3 Electrochemistry of Carbon Nanotube

Carbon nanotube not only has the shiniest behavior in stored energy, but also has new development in sensing such as biological sensors and etc. [88]. Liu [89] used moist chemical method to grow the silver nano particles on the surface of arraying carbon nanotubes. Tzeng et al. used the conductive characteristic of carbon nanotubes to produce the electrode substrate which was deposited multi-walled carbon nanotubes was deposited on aluminum substrate by electrochemical method [90].

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2-6-4 Supercapacitor of Carbon Nanotube

2-6-4-1 The Supercapacitor Electrode Mixed the Polymer with Carbon Nanotube

Jurewicz and Frackowiak [91] made the supercapacitor which mixed the multi-walled carbon nanotubes with acetylene black and PVDF (Polivinylidene Fluoride).They reported that the capacitance of their supercapacitor was 163 F/g. In addition, they were also tried to add the cobalt (Co) element and magnesium oxide (MgO) in the deposition solution of multi-walled carbon nanotubes with polymer.

This electrode can produce 15~90 F/g in KOH environment [92]. Hyeok et al. [93]

did the experiment of mixing nickel (Ni), cobalt (Co), iron sulfides (FeS), single-walled carbon nanotubes, and Ppy (Polypyrrole) under 100 torr. Their result showed that the electrode can produce 256 F/g. K. Lota [94] mixed the poly-3, 4-ethylenedioxythiophene (PEDOT) and multi-walled carbon nanotubes to produce the electrode material. The capacitance that they measured was 60~160 F/g. Xiao [95]

used complex multi-layer polymer systems to mix with the carbon nanotubes to produce the electrode. They reported that the capacitance was 21 F/g.

2-6-4-2 The Supercapacitor Electrode Mixed the Ruthenium with Carbon Nanotube

There are numbers of related literature about carbon nanotubes that mixed with ruthenium or ruthenium oxide. Kim [96] produced the ruthenium dioxides (RuO2) particles, and mixed with carbon nanotubes in colloid. The capacitance of this electrode was measured to be 407 F/g. Kang [97] deposited the RuO2 on the carbon

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nanotubes surface by MOCVD. Qin et al. [98] utilized the anodic alumina oxide (AAO) as the substrate to produce the carbon nanotubes. This purpose of this process is to produce the carbon nanotube with regularity. Arabale [99] did pre-acid process about carbon nanotubes that immersed carbon nanotubes at the 120℃ and 6M nitric acid for three hours. And the coating mixed hydrous ruthenium tri-chloride (RuCl3‧3H2O) with treated nano tube onto the substrate. Their capacitance was measured to be 80 F/g.

2-6-4-3 The Supercapacitor Electrode Manufactured by Other Processes of Carbon Nanotube

Kim et al. [100] mixed the alcohol with acid-treated multi-walled carbon nanotube, and sprayed that on the substrate. The capacitance they measured was 108 F/g.

Frackowiak et al. [101] utilized the multi-walled carbon nanotubes to produce the high capacitance matrix in the alkaline environment and the result was 90 F/g.

Niessen et al. utilized the cold pressing method to produce the electrode. The manufacturing process was mixed carbon nanotubes with silver powder under the 3 bar pressure. They were not only measured the BET value of electrode but also detected the cycle number of cyclic voltammetry [102].

2-7 Purification of Carbon Nanotube

The purification of carbon nanotube is important in producing the electrode of supercapacitor when carbon nanotube is used. However, there are more or less carbon particles which exist on carbon nanotube surface in any fabrication process no matter