臺灣博碩士論文加值系統

本研究利用溶膠-凝膠法(sol-gel method)成功的合成出氧化鎢奈米粒子(nano particle, WOx-p)，經過不同溫度的熱處理後，發現顏色會隨著鍛燒溫度的上升而產生明顯的變化，其粉末會由未經過熱處理的藍色(WOnon-p)變成黃色的氧化鎢(WO400-p)。在空氣中經鍛燒400oC後可形成具有良好結晶結構之氧化鎢奈米粒子(WO400-p)，比表面積為35.9 m2/g。在0.5M的H2SO4電解液中以掃瞄速度25mV/s、操作電位-0.3V~0.5V vs. Ag/AgCl進行循環伏安掃描，其比電容值為53.7F/g，且循環穩定性可高達500圈(以產氫反應發生與否為判斷依據) 。經過高掃描速率500mV/s的電容測試，其比電容值下降了60%。
為了能更加有效的利用氧化鎢奈米粒子，我們期望將氧化鎢奈米粒子以均勻不堆積的方式成長在工作電極上，本研究以具有高導電性(片電阻0.0013Ω/cm2) 、高比表面積(546.4m2/g) 的碳氣凝膠作為骨架，利用濕式含浸法(wet impregnation method) 將氧化鎢奈米粒子(WOnon-p) 以薄薄一層的方式成長於碳氣凝膠骨架之表面上。此複合材料在空氣中經過400oC高溫鍛燒六小時後成為具有良好的結晶結構且比表面積高達710m2/g的氧化鎢/碳氣凝膠複合材料。在0.5M的H2SO4電解液中，掃描速率為25mV/s、操作電位-0.3V~0.5V vs. Ag/AgCl進行循環伏安掃描，扣除碳氣凝膠之貢獻後氧化鎢之比電容值可高達700F/g 。在高掃描速率500mV/s下，循環穩定性至少可達4000圈，比電容值相較於25mV/s的掃描速率而言也僅僅降低31.3%，表示本複合材料具有良好的高速性能 (high rate capacity)。
本研究認為利用濕式含浸法將氧化鎢奈米粒子與碳氣凝膠結合，確實能藉由碳氣凝膠將氧化鎢奈米粒子更均勻且薄的分散在工作電極表面。由於氧化鎢奈米粒子以薄薄一層的方式分散在多孔性的碳氣凝膠骨架上，故能增加電解液與氧化鎢奈米粒子的接觸機會。當我們成長相同量的活性物質於工作電極表面時，本複合材料能更有效的利用到每一個氧化鎢奈米粒子。當電化學反應發生時，在電解液與電極表面發生法拉第反應，電子能快速地透過高導電性的碳氣凝膠傳達至電流收集器上，進而提高氧化鎢奈米粒子的使用效率。
由於本複合材料在掃描速率25mV/s下，當掃描圈數到達第500圈時工作電極表面會有氫氣產生的現象；為了延緩氫氣產生的現象發生，本研究在電解液中加入了不同濃度的碳酸氫鈉(sodium hydrogen carbonate, NaHCO3)。經過循環伏安掃描實驗發現，提升Na+的濃度確實可以延緩氫氣產生的現象發生，但卻會減少複合材料的比電容值，在碳酸氫鈉之濃度為0.06M時，掃描速率為25mV/s下，比電容值減少為620F/g，但循環穩定性卻可高達至少1000圈。
利用氧化鎢/碳氣凝膠所製備而成的對稱式電容器，經過不同電流密度進行充放電的實驗後，其充放電圖形大約對稱，但比電容值偏低且iR drop亦會隨著電流密度的上升而增加。經過公式計算後，得到比能量以及比功率的值分別為：2 Wh/kg、6.23kW/kg，具有成為下世代電容器的潛力。

Tungsten trioxide, a low cost and an environmentally friendly supercapacitive material, is deposited as a thin nanostructure of nanocrystals into carbon aerogels, a mesoporous host template of high specific surface areas and high electric conductivities, with a wet chemistry process. This tungsten trioxide/carbon aerogel composite shows ultrahigh specific capacitances(tungsten trioxide based) of around 700 F/g at a scan rate of 25 mV/s within a potential window of -0.3 to 0.5 V in 0.5M H2SO4 solutions. The composite also possesses an excellent high rate capability manifested by maintaining specific capacitances above 480 F/g at a high scan rate of 500 mV/s, and an outstanding cycling stability demonstrated by a negligible 5% decay in specific capacitances after 4000 cycles.
The success is attributable to the fuller utilization of tungsten trioxide for supercapacitance generation, made possible by the composite structure enabling largely and well exposed tungsten trioxide to the electrolyte and easy transport of charge carriers, ions and electrons, within the composite electrode.
Plain tungsten trioxide electrodes are also investigated. The as-prepared tungsten trioxide nanoparticles are synthesized with a sol-gel process, followed by calcination at 400 oC. The specific capacitances of plain tungsten trioxide electrodes are 53.7F/g at a scan rate of 25mV/s within a potential window of -0.3 to 0.5 V in 0.5M H2SO4 solutions. When the scan rate is increased to 500mV/s, the specific capacitances of the plain tungsten trioxide electrode decrease by 60%.
Symmetric capacitors composed of two tungsten trioxide/carbon aerogel composite electrodes are studied. The specific energy and specific power of this device equal 2Wh/kg and 6.2kW/kg, respectively.
The products have been characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM),X-ray spectroscopy (XPS), wide angle X-ray scattering (WAXS), surface area and pore size analyses (BET), and cyclic voltammetry (CV).

摘要 i
Abstract iii
總目錄 V
圖目錄 VII
表目錄 XIII
第一章 緒論 1
1.1電化學原理 1
1.1.1 電化學反應系統 1
1.1.2影響電化學反應系統的因素 2
1.1.3電極材料 3
1.2 氣凝膠之介紹 4
1.2.1氣凝膠簡介 4
1.2.2氣凝膠之製備 5
1.2.3二氧化碳超臨界乾燥系統 8
1.3電化學電容器 10
1.3.1電化學電容器簡介 10
1.3.2擬電容器 12
1.3.3電容測試原理 13
第二章 文獻回顧 18
2.1 利用溶劑法製備氧化鎢 18
2.1.1利用熱溶法(solvothermal method)合成氧化鎢奈米線 18
2.1.2利用微波輔助水熱法合成氧化鎢及水合氧化鎢混合物 24
2.2 利用電化學方法製備氧化鎢 28
2.3 利用溶膠-凝膠法製備氧化鎢奈米粒子 36
第三章 研究方法 41
3.1 實驗藥品 41
3.2 實驗儀器 43
3.3 檢測儀器 44
3.4 實驗動機 46
3.5 實驗流程 47
3.5.1 石墨電極之製備及前處理 48
3.5.2 氧化鎢奈米粒子之製備 49
3.5.3 碳氣凝膠之製備方法 51
3.5.4 利用濕式含浸法沉積氧化鎢於碳氣凝膠骨架上 52
3.5.5 氧化鎢奈米粒子、氧化鎢/碳氣凝膠之石墨工作電極製備 54
3.5.6 電化學分析實驗 54
第四章 實驗結果與討論 57
4.1利用溶膠-凝膠法製備氧化鎢奈米粒子之結果與討論 57
4.2 氧化鎢/碳氣凝膠複合材料之結果與討論 65
4.2.1 氧化鎢/碳氣凝膠複合材料之材料鑑定 65
4.2.2 氧化鎢/碳氣凝膠複合材料之電化學實驗 73
第五章 結論 89
第六章 參考資料 91

1. Tewari, P.H., A.J. Hunt, and K.D. Lofftus, Ambient-temperature supercritical drying of transparent silica aerogels. Materials Letters, 1985. 3(9-10): p. 363-367.
2. Pierre, A.C. and G.M. Pajonk, Chemistry of Aerogels and Their Applications. Chemical Reviews, 2002. 102(11): p. 4243-4266.
3. Hu, C.-C., et al., Design and Tailoring of the Nanotubular Arrayed Architecture of Hydrous RuO2 for Next Generation Supercapacitors. Nano Letters, 2006. 6(12): p. 2690-2695.
4. Wang, D., et al., Hexagonal mesocrystals formed by ultra-thin tungsten oxide nanowires and their electrochemical behaviour. Chemical Communications, 2010. 46(41): p. 7718-7720.
5. Chang, X., et al., Assembly of tungsten oxide nanobundles and their electrochromic properties. Applied Surface Science, 2011. 257(13): p. 5726-5730.
6. Chang, K.-H., et al., Microwave-assisted hydrothermal synthesis of crystalline WO3–WO3•0.5H2O mixtures for pseudocapacitors of the asymmetric type. Journal of Power Sources, 2011. 196(4): p. 2387-2392.
7. Baeck, S.H., et al., Controlled Electrodeposition of Nanoparticulate Tungsten Oxide. Nano Letters, 2002. 2(8): p. 831-834.
8. Szymanska, D., et al., Effective charge propagation and storage in hybrid films of tungsten oxide and poly(3,4-ethylenedioxythiophene). Journal of Solid State Electrochemistry, 2010. 14(11): p. 2049-2056.
9. Zou, B.-X., et al., Electrodeposition and pseudocapacitive properties of tungsten oxide/polyaniline composite. Journal of Power Sources, 2011. 196(10): p. 4842-4848.
10. Djaoued, Y., S. Priya, and S. Balaji, Low temperature synthesis of nanocrystalline WO3 films by sol–gel process. Journal of Non-Crystalline Solids, 2008. 354(2–9): p. 673-679.
11. Tong, M., G. Dai, and D. Gao, WO3 thin film sensor prepared by sol–gel technique and its low-temperature sensing properties to trimethylamine. Materials Chemistry and Physics, 2001. 69(1–3): p. 176-179.
12. Cheng, W., et al., Synthesis and electrochromic properties of mesoporous tungsten oxide. Journal of Materials Chemistry, 2001. 11(1): p. 92-97.
13. Li, J., et al., Studies on preparation and performances of carbon aerogel electrodes for the application of supercapacitor. Journal of Power Sources, 2006. 158(1): p. 784-788.
14. Wei, T.-Y., et al., Cobalt Oxide Aerogels of Ideal Supercapacitive Properties Prepared with an Epoxide Synthetic Route. Chemistry of Materials, 2009. 21(14): p. 3228-3233.
15. Deepa, M., et al., Annealing induced microstructural evolution of electrodeposited electrochromic tungsten oxide films. Applied Surface Science, 2005. 252(5): p. 1568-1580.
16. Granqvist, C.G., Electrochromic tungsten oxide films: Review of progress 1993-1998. Solar Energy Materials and Solar Cells, 2000. 60(3): p. 201-262.
17. Khalfaoui, M., et al., New theoretical expressions for the five adsorption type isotherms classified by BET based on statistical physics treatment. Journal of Colloid and Interface Science, 2003. 263(2): p. 350-356.
18. Chen, L., et al., CeO₂–WO₃ Mixed Oxides for the Selective Catalytic Reduction of NO_x by NH₃ Over a Wide Temperature Range. Catalysis Letters, 2011. 141(12): p. 1859-1864.
19. Yang, H., D. Zhang, and L. Wang, Synthesis and characterization of tungsten oxide-doped titania nanocrystallites. Materials Letters, 2002. 57(3): p. 674-678.
20. Tomova, D., et al., Photocatalytic oxidation of 2,4,6-trinitrotoluene in the presence of ozone under irradiation with UV and visible light. Journal of Photochemistry and Photobiology A: Chemistry, 2012. 231(1): p. 1-8.
21. Ham, D.J., et al., Hydrothermal synthesis of monoclinic WO3 nanoplates and nanorods used as an electrocatalyst for hydrogen evolution reactions from water. Chemical Engineering Journal, 2010. 165(1): p. 365-369.
22. Phuruangrat, A., et al., Synthesis of hexagonal WO3 nanowires by microwave-assisted hydrothermal method and their electrocatalytic activities for hydrogen evolution reaction. Journal of Materials Chemistry, 2010. 20(9): p. 1683-1690.
23. Song, Y.-Y., et al., Multistage Coloring Electrochromic Device Based on TiO2 Nanotube Arrays Modified with WO3 Nanoparticles. Advanced Functional Materials, 2011. 21(10): p. 1941-1946.
24. Brennan, M.P.J. and O.R. Brown, Carbon electrodes: Part 1. Hydrogen evolution in acidic solution. Journal of Applied Electrochemistry, 1972. 2(1): p. 43-49.
25. Moreno-Castilla, C. and F.J. Maldonado-Hódar, Carbon aerogels for catalysis applications: An overview. Carbon, 2005. 43(3): p. 455-465.
26. Pröbstle, H., M. Wiener, and J. Fricke, Carbon Aerogels for Electrochemical Double Layer Capacitors. Journal of Porous Materials, 2003. 10(4): p. 213-222.
27. Fischer, A.E., et al., Incorporation of Homogeneous, Nanoscale MnO2 within Ultraporous Carbon Structures via Self-Limiting Electroless Deposition:  Implications for Electrochemical Capacitors. Nano Letters, 2007. 7(2): p. 281-286.
28. Hu, C.-C., Y.-T. Wu, and K.-H. Chang, Low-Temperature Hydrothermal Synthesis of Mn3O4 and MnOOH Single Crystals: Determinant Influence of Oxidants. Chemistry of Materials, 2008. 20(9): p. 2890-2894.
29. Du, X., et al., Electrochemical Performances of Nanoparticle Fe3O4/Activated Carbon Supercapacitor Using KOH Electrolyte Solution. The Journal of Physical Chemistry C, 2009. 113(6): p. 2643-2646.
30. Dini, D., F. Decker, and E. Masetti, A comparison of the electrochromic properties of WO₃ films intercalated with H⁺, Li⁺ and Na⁺. Journal of Applied Electrochemistry, 1996. 26(6): p. 647-653.
31. Turyan, I., et al., Studying electron transfer at electrochromic tungsten oxide sol-gel films with scanning electrochemical microscopy (SECM). Physical Chemistry Chemical Physics, 2003. 5(15): p. 3212-3219.
32. Patel, K.J., et al., An investigation of the insertion of the cations H+, Na+, K+ on the electrochromic properties of the thermally evaporated WO3 thin films grown at different substrate temperatures. Materials Chemistry and Physics, 2010. 124(1): p. 884-890.
33. Hung, P.-J., et al., Ideal asymmetric supercapacitors consisting of polyaniline nanofibers and graphene nanosheets with proper complementary potential windows. Electrochimica Acta, 2010. 55(20): p. 6015-6021.
34. Jeong, Y.U. and A. Manthiram, Amorphous Tungsten Oxide/Ruthenium Oxide Composites for Electrochemical Capacitors. Journal of The Electrochemical Society, 2001. 148(3): p. A189-A193.
35. Khomenko, V., E. Raymundo-Piñero, and F. Béguin, Optimisation of an asymmetric manganese oxide/activated carbon capacitor working at 2 V in aqueous medium. Journal of Power Sources, 2006. 153(1): p. 183-190.
36. Brinker,C.J. and G.W. Scherer,Sol-Gel Science.＂The Physics and Chemistry of Sol-Gel
Processing,＂Academic Press, New york (1999)
37. Newman,J.,＂Electrochemical systems,＂Prentice-Hall,N.J. (1972)
38. Pierre,A.C. and G.M. Pajonk, ＂Chemistry of aerogels and their applications,＂Chem.
Rev.,102,4243, (2002)
39. Pletcher,D.,＂Industrial electrochemistry,＂CHAPMAN &; HALL,N.Y. (1984)
40. Jeffrey W. Long,” Asymmetric electrochemical capacitors—Stretching the limits of aqueous
electrolytes,” MRS Bulletin, vol 36, (2011)
41. 林佑勳,＂含氧化錳複合氣凝膠在超級電容器之應用＂,國立清華大學化工研究所碩士
論文,(2010)
42. 簡馨綺,＂以容膠凝膠法製備氧化鎳鈷氣凝膠及其複合材料於產氫及儲能之應用＂國立清華大學化工研究所碩士論文,(2011)
43. 洪卿雲,＂以脈衝-休止法製備錳氧化物奈米線應用於超級電容器,＂國立清華大學化工
研究所碩士論文,4-5(2009)
44. 張光輝,＂循環伏安法製備含水釕銥氧化鎢於電化學電容器的應用,＂國立中正大學化
工研究所碩士論文,2(2000)
45. 盧偉珠,＂高校的金屬氧化物氣凝膠觸媒,＂化工資訊,四十八期, 58-65(2001)
46. 魏得育和呂世源,＂最輕的固體 氣凝膠,＂科學發展, 402期, 60-65 (2006)