脫層蒙脫石與二氧化鈦奈米複合材料之研製及其在固態染料敏化太陽能電池之應用

Fabrication and Characterization of Exfoliated Montmorillonite/Titanium Dioxide Nanocomposites and Their Application on Solid-State Dye Sensitized Solar Cell

蔡竣凱(Chun-Kai Tsai)

指導教授 ： 林金福

國立臺灣大學/工學院/高分子科學與工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.11248

摘要

本實驗室過去發現以無乳化劑聚合法製備的脫層蒙脫石(exMMT)添加至防曬乳液中對皮膚有抗氧化能力，在染料敏化太陽能電池應用中甚至可將電解液的I-氧化至I5-，因此本論文進一步探討exMMT吸引電子的能力。首先將蒙脫石(MMT)分別以陰離子(無乳化劑乳化聚合)和陽離子(帶陽離子胺鹽的長鏈分子)脫層法將其脫層，從TEM觀察中得知exMMT的大小均介於數百奈米之間，並從TGA結果計算脫層劑殘留量約0.1~0.3 g/g-exMMT。接著利用exMMT具有吸附胺基的特性來吸附胺基酸。由TGA結果得知陰離子脫層法之exMMT的胺基酸吸附量隨胺基酸添加量增加而下降，而陽離子脫層法之exMMT則反之。另外以FTIR觀察胺基酸官能基變化，在陰離子脫層法之exMMT中可發現-NH3+ 官能基特徵峰，而陽離子脫層法者因具有相同官能基覆蓋了其訊號；-COOH官能基特徵峰因陰離子脫層法之exMMT具有脫層劑PMMA的訊號而被覆蓋，陽離子脫層法者則可被觀察到。接著從TEM觀察到二氧化鈦顆粒與胺基酸官能基-COOH相互吸引而成功吸附於exMMT而得到exMMT/TiO2複合材料，輔以元素分析及繞射圖譜加以驗證。在亞甲基藍添加exMMT/TiO2複合材料之光催化實驗中，從紫外光可見光譜與螢光放光光譜觀察到exMMT具抓二氧化鈦之光電子的能力進而抑制其降解亞甲基藍的催化能力，其中含有陰離子脫層法之exMMT的複合材料效果較好。固態染料敏化太陽能電池的應用中，將exMMT/TiO2複合材料添加至元件的不同位置並觀察元件表現。實驗結果顯示複合材料位於二氧化鈦多孔層之上或是位於二氧化鈦緻密層之上的元件，在照光下能使二氧化鈦能隙上升、開路電壓(Voc)變大及電子生命週期(τIMVS)變長；而添加一層複合材料在FTO導電玻璃之上可吸引電子並快速導入FTO導電玻璃使短路電流(Jsc)上升，且電子傳遞週期(τIMPS)變短，光電轉換效率從0.691 ± 0.035 % 上升至0.719 ± 0.046 %。此外，在交流阻抗分析觀察到照光時阻抗變小，未照光時阻抗變大，表示複合材料對於不同方向的電子具有整流效果。

關鍵字

蒙脫石 ； 二氧化鈦 ； 複合材料 ； 光催化 ； 固態染料敏化太陽能電池

並列摘要

A novel method using the soap-free emulsion polymerization to exfoliate mortmorillonite (MMT) was discovered by our laboratory. We found that sunscreen with the addition of exfoliated MMT (exMMT) can protect skin from getting oxidized. By using exMMT to gel the ionic liquid electrolyte for dye sensitized solar cell (DSSC), I- was oxidized to I3- and I5- improving the charge transportation. As a result, to investigate the properties of exMMT associated with the attraction of photoelectrons was the main objective of this master thesis. Also, exMMT was farbricated by exfoliating MMT with a kind of amine-terminated polymer in order to compare the results with soap-free emulsion polymerization method. TEM images indicated that the size of exMMT was ~300 nm in width. Because exMMT has a strong affinity for amine group, FTIR was used to analyze the adsorption of amino acid by exMMT. The results showed that the peak of –NH3+ was observed for the samples with exMMT prepared by the anionic method, but not by the cationic method which had the same –NH3+ functional group; however, the peak of –COOH exhibited the opposite result which was found for the exMMT prepared by the cationic method, but not by the anionic method. Next, from the TEM image, we found that TiO2 nanoparticles were successfully adsorbed on exMMT/amino acid to form an exMMT/TiO2 composite with aid of –COOH functional groups, which were further comfirmed by EDS measurement and X-ray diffraction pattern. After that, methyl blue solution with exMMT/TiO2 composites was exposed to ultraviolet lamp for different time. These PL and UV-vis spectra of methyl blue demonstrated that composite could hindered photodegradation reaction due to that exMMT has strong affinity to the photoelectrons produced by TiO2. In the last part, the performance of solid-state dye sensitized solar cell (SSDSSC) with exMMT/TiO2 composite layers inserting at different location of TiO2 photoelectrode were investigated. The results showed that composites located on the top of porous TiO2 layer or dense TiO¬2 layer within TiO2 photoelectrode had higher Voc and longer τIMVS due to the increase of energy band gap ; whereas one layer of composites deposited on top of the FTO glass within TiO2 photoelectrode exhibited higher Jsc and shorter τIMPS. It could be deduced that electrons attracted by composites were easier to transport into FTO conducting glass. Therefore, the power conversion efficiency increased from 0.691 ± 0.035 % to 0.719 ± 0.046 %. Besides, electrochemical impedance spectroscopy (EIS) results showed that the impedance decreased under sunlight but increased in the dark, suggesting that composites could rectify the electrons.

並列關鍵字

Mortmorillonite ； TiO2 ； composite ； photocatalysis ； SSDSSC

參考文獻

83. 蕭鈞瀚,“以聚電解質/奈米碳管複合材料製作軟質固態電解質在染料敏化太陽能電池上之應用”，國立臺灣大學材料科學與工程學研究所，碩士論文,2014.

88. 文克剛," 可交聯光敏劑與雙成份離子溶液電解質在染敏太陽能電池光電性質之研究",台灣大學高分子科學與工程研究所 碩士論文,2010

92. 程宥鈞," 以陰離子和陽離子脫層蒙脫石製備離子液體複合材料之製程及阻抗分析",台灣大學工學院材料科學與工程學研究所碩士論文 2013

3. Giannelis, E. P., Advanced Materials 1996, 8 (1), 29-35.

12. Lin, J.J.; Cheng, I. J.; Wang, R.; Lee, R.J. Macromolecules 2001, 34 (26), 8832-8834.