吳乃立臺灣大學：化學工程學研究所郭信良Kuo, Shin-LiangShin-LiangKuo2007-11-262018-06-282007-11-262018-06-282006http://ntur.lib.ntu.edu.tw//handle/246246/52307在本論文的第一部分，分別利用含浸法及循環伏安沈積法製備二氧化釕(RuO2)/二氧化錫(SnO2)複合超高電容器。針對含浸法所製備之複合電極，透過鍛燒溫度及RuO2負載之調整，該電極在1M KOH電解液中之電化學特性已被最佳化。結果顯示，當包含1.4% RuO2的複合電極經200oC鍛燒後，該電極可提供一最大RuO2貢獻比電容量約為710 F/g-RuO2。而在較高的RuO2負載時，推測其可能造成均勻成核而致使RuO2奈米微結晶總比表面積的縮減。另一方面，經最適溫度(150 oC)之熱處理程序，電鍍法製備而得的複合電極在1 M硫酸溶液中則可提供一RuO2貢獻比電容量高達930 F/g-RuO2，且在功率密度為1.5 kW/kg之操作條件下可得一能量密度約為0.5 Wh/kg。其他對照研究指出，此一複合電極相較於RuO2電鍍在平整之鈦片或多孔性導電碳黑時擁有更佳之電容表現。 另外，利用共沈法成功地製備MnFe2O4、Fe3O4、CoFe2O4以及NiFe2O4等鐵氧體材料(ferrites)，且該材料在NaCl水溶液中之電容行為亦被測試。本研究發現除了MnFe2O4具有偽電容量外，其他材料並無此一特性，且該偽電容行為僅發生在具微結晶相之MnFe2O4中，而在非晶相中則未被發現。MnFe2O4/CB複合電極在氯化鹽、硫酸鹽及亞硫酸鹽水溶液中皆表現出偽電容性質，其中在NaCl系統能提供最大之電容量。根據計算，MnFe2O4成分可提供一超過100 F/g-MnFe2O4之貢獻比電容量，以及一超過10 kW/kg之高功率輸出能力。針對氯化鹽水溶液系統，臨場X光近緣吸收光譜分析進一步證實該偽電容牽涉一在Mn和Fe的電荷轉移程序，其中主要是由佔據尖晶石結構之四面體位置的Mn所貢獻，且該電荷轉移伴隨著質子化反應或是電解液陽離子的嵌入反應。另外，複合電極在1.0 V的操作電壓下會有一約為10 mA/g的漏電流。而相較於非晶型的二氧化錳(MnO2)超高電容器，MnFe2O4可提供一較佳的循環穩定性以及一較緩慢的自放電速率。針對共沈法所製備的MnFe2O4/CB複合材料，在MnFe2O4和CB的重量比為7:3時可得到最佳電容值。 此外，MnO2·nH2O在LiCl、NaCl、KCl、CsCl以及CaCl2之鹽類水溶液中的偽電容儲電反應亦被進一步地研究。微結晶的二氧化錳薄膜及粉末經證實皆具有e-MnO2的晶相。臨場X光繞射分析顯示，在MnO2進行氧化/還原反應過程中，Mn離子的電荷轉移牽涉一陽離子在整體氧化物結構中的嵌入/遷出程序，並伴隨一可逆之晶格膨脹/收縮。另外，電化學石英晶體微天平及X光光電子光譜分析進一步指出，在所有系統中，H3O+在整體嵌入反應中扮演一主要的角色(> 60 %)，且陽離子嵌入量隨著離子大小的增加有先減少而後遞增的趨勢。該儲電反應可描述如下： Mn(IV)O2-nH2O +δe- + δ(1-f)H3O+ δf M+-->(H3O)δ(1-f)Mδf[Mn(III)δMn(IV)1-δ]O2·nH2O, 其中M+為鹼金族陽離子。In the first part of the thesis, RuO2-SnO2 composite supercapacitors were synthesized via both the impregnation and cyclic voltammetric deposition. The RuO2-impregnated SnO2 xerogel was optimized for its electrochemical capacitance in aqueous 1 M KOH electrolyte by adjusting the calcination temperature and the RuO2 loading. A specific RuO2 capacitance of 710 F/g-RuO2, is obtained with a RuO2 loading of 1.4 wt. % and by calcination at 200 oC. Higher loadings presumably result in a homogeneous nucleation, causing severe reduction in the total surface area of the RuO2 crystallites. On the other hand, after the optimization of crystallization protocol (150 oC), the electroplated RuO2-SnO2 composite exhibited a specific RuO2 capacitance of 930 F/g-RuO2 in 1 M H2SO4 electrolyte and an overall specific energy of ~ 0.5 Wh/Kg at a specific power>1.5 kW/kg. Comparative studies demonstrated that this composite electrode exhibited a far superior performance than the electrodes having RuO2 similarly plated onto either smooth Ti or porous conductive carbon black. In addition, ferrites including MFe2O4 where M = Mn, Fe, Co, or Ni have been synthesized by coprecipitation methods and tested for their capacitive behaviors in aqueous NaCl solution. MnFe2O4 has been found to exhibit pseudocapacitance, while the other ferrites do not. The results indicated the pseudocapacitance was observed only for crystalline, rather than amorphous, MnFe2O4 phase. The MnFe2O4/CB composite showed pseudocapacitance in solutions of chloride, sulfate and sulfite salts of alkali and alkaline cations, with NaCl solution giving the highest capacitance. It has exhibited specific MnFe2O4 contributed capacitances of >100 F/g-MnFe2O4 and high-power delivering capabilities of >10 kW/kg. For the chloride electrolytes, the pseudocapacitance has been identified, by in-situ X-ray absorption near edge spectroscopy study, to involve charge transfer at both the Mn and Fe sites, predominantly at the Mn ions at the tetrahedral sites of the spinel, balanced by insertion of cations from the electrolyte and protonation process. The composite electrode exhibits an operating potential window of 1.0 V with a maximum leakage current of 10 mA/g, and it exhibits superior cycling stability and reduced self-discharge rate than amorphous MnO2. The specific capacitance of the composite is a strong function of the CB content and the optimum capacitance occurs with the ferrite:CB weight ratio of 7:3. Besides, pseudocapacitive charge-storage reaction of MnO2·nH2O in several aqueous alkali and alkaline salts solutions, including LiCl, NaCl, KCl, CsCl and CaCl2, has been studied on fine-grained MnO2·nH2O thin-films and particles, which possess the e-MnO2-type crystal structure. In-situ synchrotron X-ray diffraction analysis shows that charge-transfer at Mn sites upon reduction/oxidation of MnO2·nH2O is balanced by bulk insertion/extraction of the solution cations into/from the oxide structure, which causes reversible expansion and shrinkage in lattice spacing of the oxide during charging/discharging cycles. Electrochemical quartz-crystal microbalance and X-ray photoelectron spectroscopy data further indicate that H3O+ plays the predominant (> 60%) role in all cases, while the extent of participation of alkali cations first decreases and then increases with ionic size. The charge-storage reaction can be summarized as: Mn(IV)O2-nH2O +δe- + δ(1-f)H3O+ δf M+-->(H3O)δ(1-f)Mδf[Mn(III)δMn(IV)1-δ]O2·nH2O,where M+ is alkali cation.摘要 I Abstract III Table of Contents V List of Tables IX List of Figures X Chapter 1 Introduction 1 1.1 Background 1 1.2 Motivations and Objectives 2 Chapter 2 Theory and Literature Review 4 2.1 Introduction to Electrochemical Capacitors 4 2.1.1 Classifications of Electrochemical Capacitors 5 2.1.2 Models of Electric Double Layers 10 2.1.3 Operating Characteristics of Electrochemical Capacitors 14 2.1.4 Self-discharge Mechanism of Supercapacitors 15 2.2 Development of Electrochemical Capacitors 17 2.2.1 Electrode Materials 17 2.2.2 Electrolytes 19 2.3 Introduction to Ruthenium Oxide, RuO2 21 2.3.1 Structure and Characteristics 21 2.3.2 Synthesis and Development on Supercapacitors 25 2.4 Introduction to Ferrites, MFe2O4 29 2.4.1 Structure and Characteristics 29 2.4.2 Synthesis and Development on Supercapacitors 35 2.5 Introduction to Manganese Oxide, MnO2 37 2.5.1 Structure and Characteristics 37 2.5.2 Synthesis and Development on Supercapacitors 42 2.6 Investigation on Charge Storage Mechanism of Pseudocapacitors 46 2.6.1 Ruthenium Oxide, RuO2 46 2.6.2 Manganese Oxide, MnO2 48 2.6.3 Nickel Oxide, NiO 49 2.6.4 Magnetite, Fe3O4 49 2.6.5 Cobalt Oxide, Co3O4 50 2.6.6 Molybdenum Nitride, Mo2N 51 2.7 Experimental Techniques 52 2.7.1 Electrochemical Quartz Crystal Microbalance 52 2.7.2 X-ray Absorption Spectroscopy 54 Chapter 3 Experimental 59 3.1 Synthesis of Electrode Materials 59 3.1.1 RuO2-impregnated SnO2 Xerogel 61 3.1.2 Electroplated RuO2-SnO2 Composite 61 3.1.3 Single-phased Ferrite Materials 62 3.1.4 MFe2O4/Carbon Black Composite Materials 63 3.1.5 MnO2 Powders 63 3.1.6 Electroplated MnO2 Thin Film 64 3.2 Analysis and Characterization 68 3.2.1 Phase Identification 68 3.2.2 Microstructure Characterizations 69 3.2.3 Surface Area and Pore Structure Analysis 70 3.2.4 Measurement of Chemical State 71 3.2.5 Measurement of X-ray Absorption Spectroscopy 71 3.3 Electrochemical Characterizations 75 3.3.1 Preparation of Electrodes 75 3.3.2 Cyclic Voltammetry 75 3.3.3 Chronopotentiometry 76 3.3.4 Electrochemical Quartz Crystal Microbalance 77 Chapter 4 Characterization of RuO2/SnO2 Composite Supercapacitors 79 4.1 Introduction 79 4.2 Preparation and Optimization of RuO2-impregnated SnO2 Xerogel Supercapacitor 80 4.3 Characterization of Electroplated RuO2-SnO2 Composite Supercapacitor 89 4.4 Summary 98 Chapter 5 Investigation on Capacitive Performance of Ferrite Supercapacitors 99 5.1 Introduction 99 5.2 Evaluation of Ferrite Materials as Supercapacitors 100 5.3 Basic Characterizations of MnFe2O4/Carbon Black Supercapacitors 118 5.4 Optimization of MnFe2O4/Carbon Black Composite Supercapacitors 128 5.5 Operating Characteristics of MnFe2O4/Carbon Black Supercapacitors in Aqueous Electrolytes 139 5.6 Investigation on Charge Storage Mechanism of MnFe2O4 147 5.7 Summary 156 Chapter 6 Investigation on Pseudocapacitive Charge Storage Reaction of MnO2-nH2O Supercapacitor in Aqueous Electrolytes 157 6.1 Introduction 157 6.2 Preparation of Electroplated MnO2 Thin Film 158 6.3 Investigation on Charge Storage Behavior of MnO2 162 6.4 Summary 182 Chapter 7 Conclusions 183 References 1852927423 bytesapplication/pdfen-US超高電容器偽電容機制MnFe2O4MnO2supercapacitorpseudocapacitancemechanismthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/52307/1/ntu-95-F90524002-1.pdf