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纳米复合材料的制备及其在太阳能转换中的应用
Alternative TitleThe Preparation of Nano Composites and Their Application in Solar Energy Conversion
杨乃亮
Subtype博士
Thesis Advisor王丹
2012-10-01
Degree Grantor中国科学院研究生院
Degree Discipline化学工程
Keyword氧化钛   石墨烯   石墨炔   染料敏化太阳能电池   光催化
Abstract能源问题是关乎人类未来与发展的核心问题,而解决能源问题的途径无外乎开发新能源与更高效的利用现有能源。我们将研究目光集中在绿色无污染的太阳能上,其中设计高效的纳米复合材料是提升太阳能转换效率的有效方式之一。本论文从增强电荷传输能力以及提升光的利用率两方面着手,设计制备了一系列纳米复合体系,并应用于染料敏化太阳能电池组件和光催化中。具体研究内容如下: 首先,我们将石墨烯引入到染料敏化太阳能电池中,从而提升了电荷分离能力,延长了电子寿命,抑制了复合,同时在一定程度上提升了光的利用率,进而在整体上使光生电流提升了45%,光电转换效率提高了39%。 第二,为了进一步揭示氧化钛-石墨烯之间的电荷输运行为,我们向自然界中的光合作用学习,把光合作用的光电转换过程翻译为化学语言,并从结构到功能对基粒进行模仿,通过层层自助装的方法构建了人造的氧化钛-石墨烯垛叠结构。通过对垛叠结构的光电行为进行分析,发现氧化钛-石墨烯复合薄膜往往表现出更高的光电转换能力,在薄膜厚度达到25个结构单元时,光生电流是同样条件下普通氧化钛薄膜的20倍;重要的是,通过测试我们发现电流方向会发生反转,即当薄膜较薄时,电极往往表现出阴极光电流,只有当薄膜达到一定厚度,才会产生阳极光电流,进而对外供电。同样,我们也成功制备了聚苯胺-氧化石墨垛叠结构,氧化石墨同时起到模板和掺杂剂的作用。 第三,从提升光的利用率方向着手,将表面等离子体共振效应引入染料敏化太阳能电池之中。发现拓扑结构金膜的加入可以有效的提升光的漫反射进而提升电池对光的吸收,尤其是在染料难以利用的长波段。这种更强的光利用率,可以使光电转换效率提升18%左右,并且该方法具有普适性,即不影响光阳极的结构,也不影响光阳极的电子输运行为。 最后,进行了光催化材料的改性研究。通过计算得知裸露{001}晶面的氧化钛纳米片可以与二维碳材料产生良好的复合。随后通过实验合成该纳米片,并与石墨烯、石墨炔进行复合,通过跟踪光催化降解亚甲基蓝的反应进程,发现TiO2(001)-石墨炔复合材料具有最强的光催化能力。这是由于石墨炔的引入带来了更强的电荷分离能力,更长的电子寿命,更多的杂质能级以及更强的氧化能力。
Other AbstractEnergy shortage is becoming a global and core problem nowadays, and the only two ways to solve the problem are exploring new energy and improving the avalibility of traditioanal energy. Solar energy is considered to be one of the most important energy in the future because it is highly facil and environmentally friendly. Undoubtly, the development of novel nanocomposite materials is one of the efficient approaches to increase the utilization of solar energy. Herein, we have design a series nanomaterial to enhance the photo-electric conversion by increasing the charge transport ability and the light utilization. First, we introduced graphene as 2D bridges into the nanocrystalline electrodes of dye-sensitized solar cells, which brought a faster electron transport and a lower recombination, together with a higher light scattering. On the basis of these advantages, the short-circuit current density was increased by 45% without sacrificing the open-circuit voltage, and the total conversion efficiency was 6.97%, which was increased by 39%, comparing with the nanocrystalline titanium dioxide photoanode, and it was also much better than the 1D nanomaterial composite electrode. Second, inspired by the nature, we tried to imitate the structure and function of granum. The stacked structures were fabricated with TiO2-graphene nanosheets as the thylakoids unit by layer-by-layer method, and their photo-electric effect was studied by varying the number of layers present in the film. The photo-electric response of the graphene composites are found to be 20 times higher than that of pure TiO2 in films with 25 units stacked. Importantly, the cathodic photocurrent changes to anodic photocurrent as the thickness increases, an important feature of efficient solar cells which is often ignored. Here graphene is proposed to perform similarly to the b6f complex in granum, by separating charges and transporting electrons through the stacked film. Using this innovation, stacked TiO2-graphene structures are now able to significantly increase photoanode thickness in solar cells without losing the ability to conduct electrons. Also, we extend the stacking structure fabrication into conductive polymer. With a facile method, a novel layered structure of polyaniline (PANI) with graphene oxide as the dopant and template were directly prepared. Another important method to improve the efficiency of photo-electric conversion involves increasing the light-harvesting ability. Earlier work has focused on varying the morphology of the photoanode. With such a hierarchical structured photoanode in hand, we modify herein the structure of the counter electrode to enhance the optical path length through the plasmonic and reflecttion effects. With the introduced topological gold layer, the photocurrent and efficiency are increased by 16% and 18%, respectively, due to the increased light collection. Besides, the modified counter electrode is effective at both high and low levels of solar irradiation. Finally, we extend our research into the photocatalysis. By calculating the chemical structure and electronic properties of TiO2-graphdiyne and TiO2-graphene composites by first-principles density functional theory, we found that TiO2(001)-graphdiyne composite possess good abilities of the charge separation, oxidation, and longer lifetimes of photoexcited carriers among all the TiO2-graphdiyne or TiO2-graphene composites with different facets of TiO2. Hence we predict TiO2(001)-graphdiyne composite may be a potential photocatalyst, and the succeeding photodegradation experiment supported our calculation. The TiO2 (001)-graphdiyne composite gave a 1.60 times higher photocatalytic degradation reaction kinetics rate constant than pure TiO2(001), in addition, 1.26 times higher than that of TiO2(001)-graphene composite.
Pages122
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/8304
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
杨乃亮. 纳米复合材料的制备及其在太阳能转换中的应用[D]. 中国科学院研究生院,2012.
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