| 题名 | 二氧化钛纳米材料的制备及其在太阳能转换中的应用研究 |
| 作者 | 王硕 |
| 学位类别 | 博士 |
| 答辩日期 | 2012-05-21 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 王丹 |
| 关键词 | 二氧化钛 石墨炔 光催化 染料敏化太阳能电池 光散射 |
| 其他题名 | Study on Preparation of TiO2 Nanomaterials and Their Application in Solar Energy Conversion |
| 学位专业 | 化学工程 |
| 中文摘要 | 自1972年Fujishima和Honda发现TiO2电极光解水以来，半导体光催化材料由于在环境净化及太阳能利用方面具有广泛的应用前景而成为研究的热点。在半导体材料中，TiO2由于无毒、廉价及稳定的物理化学特性等优点而被广泛应用于太阳能电池和污水处理领域。然而，由于TiO2的禁带宽度较大(锐钛矿型及金红石型二氧化钛的禁带宽度分别为3.2eV和3.0eV)，只吸收仅占太阳光极少部分的紫外光，对太阳能的利用率低。为此，本研究致力于通过设计TiO2的纳米结构来提高其太阳能利用率及光催化活性的方法研究；通过TiO2与其它材料复合来改善其性能。当TiO2与含有共轭π键的碳材料复合后，两者产生协同作用，这种作用可以拓展二氧化钛对光的吸收范围并抑制电子-空穴的复合。在本文中，通过简易的水热过程制备出TiO2与石墨炔（GD）的复合物，并研究其在光催化降解亚甲基蓝染料及在染料敏化太阳能电池中的应用。此外，还通过紫外辐照，原位诱发膜层中单体的聚合及单体和高分子的接枝制备出网状多孔TiO2薄膜。这种网状多孔薄膜具有良好的光散射效应，将其制备在P25纳米粒子层表面作为光散射层时，可较大的提高太阳能电池的光电转换效率。主要研究结果如下：（1）利用水热反应体系制备出TiO2与石墨炔（GD）复合材料，通过改变复合物中石墨炔的含量可以调控复合物的光催化活性，当石墨炔含量为0.6 wt %时光催化活性最佳。在紫外光降解亚甲基蓝的实验中，P25-石墨炔复合物表现出比纯P25、P25-碳纳米管复合材料以及P25-石墨烯复合材料更优越的光催化性能。理论研究表明，片状GD与P25纳米粒子的复合可引入C的杂质能级，缩减小了二氧化钛的带隙，扩展了光吸收范围，因此P25与GD复合物显示出优良的可见光催化活性。（2）将制备出的P25-GD复合材料作为光阳极应用于染料敏化太阳能电池中，相对于单一P25薄膜电极表现出更高的短路电流和光电转换效率，其光电转换效率达6.61%。研究表明，石墨炔这种二维片状结构的引入，加快了薄膜电极中电子的转移速度，因而利于材料中光生电子的转移，降低光生电子和空穴的复合，从而提高其光电转换效率。（3）通过紫外辐照法制备出具有网状结构的二氧化钛多孔薄膜，可将其作为光散射层置于P25纳米粒子层上，组成具有双层结构的组合电池。紫外-可见漫反射光谱的研究表明这种双层结构薄膜具有比相同厚度的单一P25薄膜更优异的漫反射性能。光电性能研究显示，组合电池光电转换效率达6.95 %，比单一P25薄膜电池效率提高了近11.2 %。 |
| 英文摘要 | Semiconductor photocatalytic materials have been intensively investigated for their wide potential application in water purification and solar energy conversion since Fujishima and Honda discovered the photocatalytic splitting of water on TiO2 electrodes in 1972. Among the various semiconductors, titanium oxide has been extensively studied for the wastewater treatment and solar energy conversion due to its relative non-toxicity, low cost, and stable physical and chemical properties. {Sun, 2008 #2}However, the large intrinsic band gap of titanium oxide (3.2 eV for anatase and 3.0 eV for rutile) means that TiO2 nanoparticles can only utilize the small ultraviolet fraction of solar light. Therefore, other materials have been extensively researched in order to form composite materials with TiO2. These materials aim to improve the performance of TiO2 to meet new requirements imposed by specific applications, such as solar energy utilization and heterogeneous photocatalysis. Carbon based materials with conjugated π systems can often induce synergistic or cooperative effects between the metal oxide and carbon phases. These materials can be used to expand the light absorption range or suppress electron-hole recombination. In the present work, we prepared nanocomposites of P25-graphdiyne by a facile hydrothermal treatment and used these composite products as photocatalyst in the degradation of methylene blue and photoanode in the dye-sensitized solar cells. Furthermore，porous TiO2 films with net-like framework were prepared by UV irradiation induced in situ polymerization of organic monomer and graft-polymerization to macromolecule reaction. The light scattering property of porous TiO2 films with net-like framework makes it a promising candidate for use as the scattering layer in dye sensitized solar cells. A bilayer structured photoelectrode consisting of the porous TiO2 films with net-like framework as a scattering layer on top of the benchmark P25 film was fabricated and studied as dye-sensitized solar-cell photoanodes. It has mainly the following aspects: （1）Titania nanoparticles (P25) are successfully chemically-bonded with graphdiyne (GD) nanosheets by a facile hydrothermal treatment. The photocatalytic activity of P25-GD could be adjusted by changing the content of GD in composites and the optimized value is about 0.6 wt %. The as-prepared P25-GD nanocomposite exhibits higher photocatalytic activity for degrading methyl blue (MB) under UV irradiation, than not only P25 and P25-carbon nanotube composites but also the current well-known P25-graphene composite photocatalysts. Moreover, P25-GD also shows considerable visible-light-driven photocatalytic activity, since the formation of chemical bonds between P25 and GD effectively decreases the band gap of P25 and extends its adsorbable light range. （2）Dye-sensitized solar cells based on photoanode materials from the prepared P25-GD nanocomposite exhibit a power conversion efficiency of 6.61%. Superior photocurrent and power conversion efficiency for the P25-GD nanocomposite compared to the P25 nanoparticles is a consequence of a lower recombination and a faster electron transport with the introduction of graphdiyne chiefly. Graphdiyne with a special 2D structure are bound to TiO2 could conduct photoelectrons easily, while the electrons were generated from TiO2 under light irradiation. Thus, the efficiency of the electron-hole recombination in the nanocomposite may be decreased. （3）The porous TiO2 films with net-like framework have been successfully prepared by a UV irradiation method followed by calcination. We fabricated a bilayered photoanode by introducing porous TiO2 films with net-like framework layer on the P25 nanocrystalline layer to improve the cell performance. UV-Vis demonstrated that the light-harvesting efficiency of the bilayer light-scattering electrode film was better than that of the benchmark P25 film due to the effectively light-scattering structure. The overall energy-conversion efficiency (η) of 6.95% was achieved by the formation of bilayered TiO2 film, which is 11.2% higher than that formed by P25 alone. |
| 语种 | 中文 |
| 公开日期 | 2013-09-25 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1852]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 王硕. 二氧化钛纳米材料的制备及其在太阳能转换中的应用研究[D]. 中国科学院研究生院. 2012. |
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