二氧化鈦空心球之製備與應用

本研究中，我們先利用簡單的一步水熱法製備二氧化鈦空心球(TiHS)。經由粉末式X射線繞射儀、氮氣等溫吸脫附技術、場發射掃描式電子顯微鏡以及穿透式電子顯微鏡等進行特性鑑定，此方法所製備出之TiHS結構呈現銳鈦礦晶相、比表面積為66~143 m2/g、空心球的直徑約為1 μm。並且更進一步將製得之TiHS應用於染料敏化太陽能電池上。我們先將二氧化鈦空心球配成漿料後，塗佈於透明導電電極上，形成膜厚為5 μm與9 μm的薄膜作為染料敏化太陽能電池之光陽極，以N719染料作為敏化劑，然後在AM 1.5的模擬太陽光照射下(100 mW/cm2)進行測試，其光電轉換效率分別為3.85%與5.50%。由於文獻中曾提及若添加大尺寸的二氧化鈦可以增加入射光之散射與光的利用率，進而提升染料敏化太陽能電池的光電轉換效率，因此，我們以溶膠-凝膠法所製備之二氧化鈦奈米粒子(TiO2-SG)作為傳輸層，於上方分別塗佈厚度為8 μm的二氧化鈦空心球薄膜，以N719染料作為敏化劑，在AM 1.5的模擬太陽光照射下(100 mW/cm2)進行測試，其光電轉換效率為7.15%，相較於未加散射層之TiO2-SG的光電轉換效率6.21%提高1.15倍。另外，將TiO2-SG與二氧化鈦空心球進行物理混合後作為TiO2-SG的散射層，可得光電轉換效率為7.29 %，其相較未物理混合之二氧化鈦空心球之效率提高約1.02倍，原因為添加TiO2-SG可以增加散射層對染料的吸附量，也可以使電子傳遞更為順暢。為了改善傳統水熱耗時久的問題，我們改微波輔助水熱法來製備二氧化鈦空心球(TiHS-MW)，此法大幅縮短了製備所需之反應時間。經由各式物理特性鑑定。TiHS-MW結構為銳鈦礦晶相、比表面積為98 m2/g、空心球體大小為1 μm。亞甲基藍脫色實驗中顯示，TiHS-MW之光脫色效能和TiHS相符。另外，在微波輔助水熱法製備二氧化鈦空心球的過程中加入硝酸鎘，再將合成出之粉體分散於硫化鈉水溶液中，會得到含有硫化鎘之二氧化鈦空心球。於亞甲基藍的脫色實驗中發現含有5 wt%之硫化鎘的二氧化鈦空心球有最佳的染料吸附特性，因此，亦有最佳的亞甲基藍脫色速率。接著探討經表面修飾後之TiHS-MW於氫氣儲存上之應用。我們利用光沉積法製備含有1 wt%之鈀或1 wt%鉑的二氧化鈦空心球，將其應用於氫氣儲存之研究。在壓力為1大氣壓時，鈀或鉑的二氧化鈦空心球其儲氫量分別為4.20%與4.02%，而當壓力在約為30大氣壓時，含鈀或鉑的二氧化鈦空心球其儲氫量分別提升至6.52%與6.36%。我們成功的利用簡單的一步水熱法製備出二氧化鈦空心球(TiHS)，將它應用於染料敏化太陽能電池作為散射層，其對整體的光電轉換效率皆有提升的效果。接著進一步改用微波輔助水熱法製備二氧化鈦空心球(TiHS-MW)，不僅成功的大幅縮短反應時間，將它應用於亞甲基藍光脫色與氫氣儲存也都有相當好的效果。

關鍵字

染料敏化太陽能電池；亞甲基藍光脫色；微波輔助水熱法；二氧化鈦空心球；氫氣儲存

並列摘要

In our research, we used a simple hydrothermal method to prepare titania hollow sphere, named TiHS. Titania hollow sphere were characterized through XRD, UV-Vis, N2 adsorption-desorption isotherms, FESEM and TEM. We could obtain some information about titania hollow sphere that possess pure anatase phase, 66~143 m2/g of surface area with 1 μm diameter. We used titania hollow sphere as photoanode for dye-sensitized solar cells. At first, we used different film thickness of titania hollow sphere for dye-sensitized solar cells. When film thickness of titania hollow sphere were 5 μm and 9 μm, we could obtain photoconversion efficiencies of 3.85% and 5.50% under AM1.5 solar irradiation (100 mW/cm2), respectively. The photoconversion efficiencies could enhance, because film thickness of titania hollow sphere increased, and titania hollow sphere promote its dye adsorption capacity. On the other hand, we used titania hollow sphere as scattering layer atop the titania nanoparticle for dye-sensitized solar cell. The photoconversion efficiency could enhance from 6.21% to 7.15% under AM1.5 solar irradiation (100 mW/cm2). Furthermore, because titania hollow sphere as scattering layer can raise light scattering property. Here, we mixed titania hollow sphere and titania nanoparticle with weight ratio 1 : 1 by physical method. We could obtain higher photoconversion efficiency of 7.29% which is obviously higher than titania hollow sphere due to the fact that the mixed of titania hollow sphere and titania nanoparticles could augment dye adsorption capacity for scattering layer. Secondly, we used microwave-assisted hydrothermal to prepare titania hollow sphere, named TiHS-MW, characterized by XRD, UV-Vis, N2 adsorption-desorption isotherms, FESEM and TEM. The titania hollow sphere prepared by microwave-assisted hydrothermal have pure anatase phase, 98 m2/g of surface area and 1 μm diameter. In addititon, we used TiHS-MW to photoblanch methylene blue. Compare this with TiHS, however, there is no distinction between TiHS and TiHS-MW. In short, it is by microwave-assisted hydrothermal that the titania hollow sphere was prepared can not only diminish reaction time but also be realistic. Thirdly, thtough depositing CdS on TiHS-MW, we made it apply to photoblanch methylene blue. Besides, we hope that CdS can mitigate electron-hole recombination on titania, obtaining better decolor constant (k). So, we could gain the best decolor constant (k) as 5 wt % CdS deposited. At last, we made 1 wt % palladium or 1 wt % platinum deposited on TiHS-MW, named Pd/TiHS-MW or Pt/TiHS-MW, by photodeposition method, making these apply for hydrogen storage. Additionally, FESEM-Mapping showed that palladium or platinum was distributed uniformly on TiHS-MW surface. It could obtain 4.20 wt % and 4.02 wt % capacity of hydrogen storage at 1 atm as we used Pd/TiHS-MW and Pt/TiHS-MW, respectively. Moreover, the capcity were 6.52 wt % and 6.36 wt % when pressure reached to 30 atm.

並列關鍵字

Photoblenching methylene blue ； Microwave-assisted hydrothermal ； One-step hydrothermal ； Titania hollow sphere ； Dye-sensitized solar cell ； Hydrogen storage

參考文獻

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二氧化鈦空心球之製備與應用

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