簡淑華Chien, Shu-Hua臺灣大學:化學研究所郭至剛Kuo, Chih-KangChih-KangKuo2010-06-302018-07-102010-06-302018-07-102009U0001-2101200917164000http://ntur.lib.ntu.edu.tw//handle/246246/187568本研究探討四氯化鈦(TiCl4)在高濃度硝酸(5 M HNO3)水溶液系統中，鈦離子濃度([Ti4+])及反應溫度對生成二氧化鈦晶相[銳鈦礦(anatase)、板鈦礦(brookite)及金紅石(rutile)]的影響。結果顯示在100 oC下，在我們所探討的[Ti4+]區間內(0.3 - 0.6M)，產物晶相皆為brookite/rutile混相。在70 oC下，當鈦離子濃度為0.3, 0.6及0.8 M時，產物晶相分別為brookite/rutile混相，anatase/brookite/rutile混相及anatase/rutile混相。我們將上述混相樣品與乙醇混合、離心後，可進一步地分離出anatase、brookite、rutile個別的純相二氧化鈦。亞甲基藍光脫色反應測試顯示三種晶相中以brookite催化活性最佳，anatase次之，rutile最差。們將anatase、brookite、rutile三種純相二氧化鈦在450 oC下鍛燒30分鐘(同染料敏化太陽能電池及光電催化水分解的電極製備條件)後進行特性鑑定。高解析電子顯微鏡(HRTEM)觀察顯示anatase呈顆粒形貌，brookite呈平板狀，而rutile呈棒狀。N2等溫吸附實驗顯示anatase、brookite及rutile的BET表面積分別為91、76及32 m2/g。紫外光可見光光譜(UV-vis)顯示三種晶相中以rutile光散射能力最佳，brookite次之，anatase最差。料敏化太陽能電池測試(模擬太陽光AM 1.5, 100 mW/cm2)顯示在相同的膜厚下，由於anatase電池所吸附染料最多(N719ads = 0.060 μmol cm-2)，故其光電轉換效率最佳(η = 4.26%)，明顯優於brookite電池的2.50% (N719ads = 0.041 μmol cm-2)以及rutile電池的1.55% (N719ads = 0.016 μmol cm-2)。於rutile及brookite擁有不錯的光散射能力，我們嘗試以溶膠凝膠(sol-gel)法製得anatase奈米顆粒(SG)作為染料敏化太陽能電池電極活性層(active layer)，探討rutile及brookite作為散射層(scattering layer)的影響。結果顯示塗佈rutile及brookite作為散射層，可使SG電池的光電轉換效率由7.09% 分別大幅提升至8.44% 及9.10%。這是因為brookite除了光散射特性佳可提高光使用率(light- harvesting efficiency)外，也有不錯的染料吸附能力。電催化分解水反應測試結果顯示anatase、brookite及rutile純相二氧化鈦電極的光電轉換效率分別為0.43%、0.87% 及0.80%。入射單色光子─電子轉換效率(incident photon-to-current efficiency, IPCE)量測顯示brookite及rutile電極的光使用率明顯優於anatase。我們由光電流隨時間衰退變化求出anatase、brookite及rutile的暫態時間(transient time)分別為0.20、0.71及0.42秒，顯示電子在brookite電極間應有較長的壽命。們利用同步輻射中心的原位X光繞射光譜(in-situ XRD)探討硫酸濃度在TiCl4/HNO3水溶液系統中對生成二氧化鈦晶相的影響。結果顯示在此系統中添加硫酸除了可抑制brookite/rutile生成及促進anatase生成之外，改變硫酸濃度亦能控制rutile及anatase生成時間順序。我們利用這種特性成功地製得以anatase作為活性層、rutile作為散射層的染料敏化太陽能電池電極(即anatase早於rutile生成於導電玻璃)，電池光電轉換效率可達4.11%。此一新穎二氧化鈦電極製備方法預期可大幅改善文獻中刮刀成膜(doctor-blade)法所需的多次重覆塗佈鍛燒製程。In this study, the influences of Ti4+ concentration and reaction temperature on TiO2 phases (anatase, brookite and rutile) formed from hydrolysis of TiCl4 in 5 M HNO3(aq) were investigated. It is found that at the temperature of 100 oC, in the [Ti4+] range between 0.3 and 0.6 M, only brookite/rutile mixed phases form. While at the temperature of 70 oC, as [Ti4+] equals to 0.3, 0.6 and 0.8 M, respectively, brookite/rutile, anatase/brookite/rutile and anatase/rutile mixed phases are obtained. Separation of mixed phases into individual pure anatase, brookite and rutile was achieved via mixing as-synthesized samples with C2H5OH followed by centrifugation. Among them, brookite exhibits the best photocatalytic activity in the photobleaching of methylene blue under 300 nm UV illumination.ure anatase, brookite and rutile samples were characterized via various instruments after calcination at 450 oC for 30 min (condition the same as the fabrication of electrode for dye-sensitized solar cell and water splitting). As revealed by HRTEM, the three phases exhibit their distinctive morphologies: nanoparticle for anatase, nanoplate for brookite and nanorod for rutile. The BET surface areas are 91, 76 and 32 m2/g, respectively. UV-vis spectra showed that the scattering abilities are in the order of rutile, brookite and anatase. hotovoltaic performance of dye-sensitized solar cells made up of anatase, brookite and rutile with the same thickness were measured under AM 1.5 (100 mW/cm2). Due to the superior capability for N719 dye adsorption (N719ads = 0.060 μmol cm-2), anatase-based cell exhibits the highest photoconversion efficiency (η = 4.26%), as compared to those of brookite- (2.50%, N719ads = 0.041 μmol cm-2) and rutile-based (1.55%, N719ads = 0.016 μmol cm-2) cells. natase nanoparticles prepared via sol-gel method (SG) were utilized as active layer and brookite/rutile, due to their better scattering abilities, as scattering layer for DSSC photoanodes. Photoconversion efficiencies were increased from 7.09% without scattering layers to 8.44% and 9.10% with rutile/brookite as scattering layers, respectively. Brookite can not only adsorb more dye but scatter incident light.hotocatalytic water splitting reaction indicated photoconversion efficiencies of pure anatase-, brookite- and rutile-based working electrodes are 0.43%, 0.87% and 0.80%, respectively. Brookite and rutile exhibit better light-harvesting efficiencies than anatase in incident photon-to-current efficiency (IPCE) measurements. Transient times of anatase, brookite and rutile calculated by photocurrent relaxation with time are 0.20, 0.71 and 0.42 s, respectively, which revealed brookite electrode has the longest electron lifetime than the other two polymorphs. he effect of H2SO4 concentration on TiO2 phases formed in TiCl4/HNO3(aq) system was studied via in-situ XRD, NSRRC. It is showed that addition of H2SO4 enables the suppression of brookite/rutile and promotion of anatase in this system, and formation orders of anatase and rutile can be well-controlled by adjusting [H2SO4]. The case that anatase emerges before rutile was chosen to fabricate TiO2/TCO electrode. Such bilayer microstructure is adopted to utilize smaller anatase to adsorb more dye and larger rutile particles to scatter incident light. The photoconversion efficiency is 4.11%, and the result demonstrates that this facile process is very promising to fabricate TiO2/TCO electrode for efficient photovoltaic devices.謝誌…………………………………………………………………………....………I要…………………………………………………………………………………...IIbstract…………………………………………………………………………....…IV錄..............................................................................................................................VI目錄..........................................................................................................................IX目錄.......................................................................................................................XIII一章 緒論…………………………………………………………………………1.1 前言…………………………………………………………………………...1.2 二氧化鈦(Titanium Dioxide)簡介……………………………………………2.3 板鈦礦(brookite)的文獻回顧與合成方法…………………………………...6.4 染料敏化太陽能電池(Dye-sensitized solar cell, DSSC)…………………….91.4.1 染料敏化太陽能電池的工作原理與影響因素…………………………10.4.2 散射層(Scattering layer)概念的應用及文獻回顧………………………14 1.5 水分解(Water splitting)製氫原理及文獻回顧……………………………...16 1.6 研究動機…………………………………………………………………….20二章 實驗方法…………………………………………………………………..21 2.1 藥品與儀器………………………………………………………………….21 2.2 以水解法製備二氧化鈦奈米粒子………………………………………….23 2.3 奈米粒子的鍛燒處理……………………………………………………….23.4 以溶膠凝膠法製備二氧化鈦奈米粒子………………..…………………...25.5 材料特性分析……………………………………………………………….262.5.1 高解析穿透式電子顯微鏡 (HRTEM)…………………………………..262.5.2 場發射掃描式電子顯微鏡 (FESEM)…………………………………..262.5.3 X-射線繞射光譜 (XRD)………………………………………………262.5.4 拉曼光譜 (Raman)………………………………………………………28.5.5 氮氣等溫吸附……………………………………………….…………...28.5.6 紫外光-可見光吸收光譜 (UV-Vis)……………………………………..28.5.7 傅立葉紅外線轉換光譜 (FT-IR)………………………………..………29.5.8 X光吸收光譜 (XAS)……………………………………………………29.5.9 光致發光光譜 (PL)……………………………………………………...30.5.10 原位X-射線繞射光譜 (in-situ XRD)…………………………………31.6 亞甲基藍光脫色(photobleaching)…………………………………………..32.7 染料敏化太陽能電池與水分解反應……………………………………….352.7.1 二氧化鈦光陽極/水分解工作電極之製備…………..…………………352.7.2 染料敏化太陽能電池與水分解反應之裝置及電化學測試……………372.7.3 染料敏化太陽能電池光陽極之染料吸附量測試....................................52三章 結果與討論..................................................................................................54.1 奈米二氧化鈦之製備及光催化活性評估………………………………….543.1.1 初合成(as-synthesized)產物的鑑定……………………………………..543.1.2 初合成產物之亞甲基藍光脫色反應……………………………………64.2 鍛燒後(calcined)產物之特性鑑定…………………………….……………71.3 染料敏化太陽能電池……………………………………………………….743.3.1 三晶相奈米薄膜之染料敏化太陽能電池性能測試結果………………743.3.2 開環電壓衰退(OCVD)與電化學阻抗(EIS)測試結果………………….763.3.3 散射特性的比較…………………………………………………………793.3.4 雙層結構光陽極………………………………………………………....833.3.5 入射單色光子-電子轉化效率(IPCE)測試結果...………………………883.3.6 活性層與散射層組合之效率最佳化….………………………………...90.4 水分解……………………...………………………………………………..923.4.1 三晶相奈米薄膜水分解測試結果………………………………………923.4.2 三晶相與商用二氧化鈦P25奈米薄膜膜厚之最佳化………………….953.4.3 入射單色光子-電子轉化效率測試結果………………………………...98.4.4 水分解反應限制步驟的探討與暫態時間(transient time )……………100四章 結論...…………………………………………………………………….103五章 未來展望…………………………………………………………………105考文獻……………………………………………………………………………106錄...……………………………………………………………………………….112 以原位X光繞射(in-situ XRD)光譜儀研究奈米二氧化鈦之生成機制……112A.1 硫酸根離子的添加對水解系統的影響………………………………...112A.2 以水解法沉積染料敏化太陽能電池光陽極薄膜…………………..…...118 二氧化鈦三晶相JCPDS圖譜…………………………………………….….1233186090 bytesapplication/pdfen-US二氧化鈦水解法板鈦礦染料敏化太陽能電池光電催化分解水titanium dioxidehydrolysisbrookitedye-sensitized solar cellphotocatalytic water spitting[SDGs]SDG7thesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/187568/1/ntu-98-R93223070-1.pdf