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二氧化钛杂化材料的设计、制备及其光催化性能研究
陈琳
学位类型博士
导师马鹏程
2015-05-29
学位授予单位中国科学院大学
学位授予地点北京
学位专业材料物理与化学
关键词Tio2光催化材料 玻璃纤维 石墨烯 聚苯胺 可见光
摘要

基于半导体材料的光催化技术被广泛用于环境污染物治理领域。在诸多的半导体材料中,二氧化钛(TiO2)具有原料易得、无毒、性能稳定等特点,显示了广阔的应用前景。但是此类材料在使用过程中普遍存在易聚集、难回收、对太阳光利用率低、量子产率低、光生电子和空穴的分离效率差等不足。 针对上述问题,本论文采用形貌调控、贵金属沉积、半导体复合等手段,来拓展TiO2光催化材料的光响应范围,促进光生载流子分离,进而提高其光催化活性。全文主要研究结果如下:(1) 分级结构TiO2/玻璃纤维复合材料:为了克服TiO2粉末在使用过程中易团聚、难分离、催化活性低等缺点,本章以廉价的玻璃纤维(GF)为载体,通过原位水解沉淀和碱性水热法,分别制备了具有分级结构的TiO2微纳球/GF和片层TiO2/GF复合物。采用多种表征手段研究了复合光催化剂的结构、晶型与表面特征之间的构效关系。研究结果表明两种分级结构复合材料在紫外光下对甲基橙(MO)和苯酚均表现出良好的催化性能,其中片层结构TiO2/GF的降解活性最高,这主要是在光催化过程中产生的羟基和过氧自由基共同作用使得MO被降解。复合材料中GF在不同条件下表现出螺纹状或片状形貌,有利于TiO2的负载并赋予光催化材料优异的循环使用稳定性。(2) 三维结构TiO2球/石墨烯复合材料(TiO2/GR):为了实现光生电子空穴的有效分离、提高TiO2的量子效率,本章以带负电的氧化石墨为石墨烯的前驱体、以带正电的钛醇分子为TiO2钛源,通过静电自组装技术在室温下合成了具有三维结构的TiO2/GR复合材料。所得材料中TiO2球穿插生长于石墨烯片层之间,形成稳定的三维导电网络结构。复合材料光催化性能评价以及光电流响应测试结果表明三维结构TiO2/GR具有良好的电荷分离效率,可在光催化反应中产生更多的活性自由基。(3) 核壳结构TiO2@聚苯胺(TiO2@PANI)光催化剂:基于充分利用太阳能方面的考虑,本章采用具有共轭π电子的导电聚合物PANI为包覆剂,制备出具有较强的可见光响应能力的TiO2@PANI核壳结构复合材料。核壳结构可以有效防止光催化材料的团聚并起到敏化TiO2的作用。所制备的TiO2@PANI复合物具有比表面积大、多孔等结构特性。材料在可见光条件下对有机物MO具有较好的光催化降解效果,这归因于材料具有良好的光生载流子分离效率。(4) 具有等离子体共振效应的Ag-AgBr-TiO2/玻璃纤维复合材料:为进一步提高TiO2的可见光催化活性,结合能带理论和复合半导体的能带位置,将具有等离子体共振效应的Ag-AgBr引入TiO2光催化体系并固载在GF表面,制备了具有多尺度结构的Ag-AgBr-TiO2/GF复合材料,该材料在可见光条件下对MO的降解速率常数达0.024 min-1,高于贵金属掺杂的TiO2 (0.0037-0.018 min-1)以及商业化P25 (0.0028-0.015 min-1,紫外光条件下);材料在使用5次后对甲基橙的脱色率仍保持在85%以上,不同材料和形貌之间的协同效应使得该催化剂具有优异的可见光催化效果。

其他摘要

Absrtract Photocatalysis based on semiconductors is regarded as a promising technology to solve the problems associated with the air and water pollution. Among numerous semiconductors, titanium dioxide (TiO2) has obvious advantages over other semiconductors due to its low cost, non-toxic and stable performance. Unfortunately, TiO2 nanoparticles tend to aggregate in suspension, leading to a rapid loss in active sites and photocatalytic capability. Besides these drawbacks, the low efficiency on separating electron-hole pairs and poor sensitivity to sunlight of material limit the wide photocatalytic applications of TiO2. This dissertation is dedicated to optimize the properties of TiO2 via various methods, including morphology controlling, doping with metal and semiconductors, to improve the separation efficiency of hole-electron pairs in the material and to enhance the photocatalytic performance of materials under the visible light. The major findings arising from this thesis are summarized as follows: 1.Hierarchical TiO2/glass fibres (GF) composites: This chapter described the preparation of hierarchical TiO2/glass fibres via the hydrolysis-precipitation and hydrothermal methods, in an effort to solve the problems associated with the agglomeration, separation and low photocatalytic performance of TiO2. The TiO2 particles on fiber surface exhibited spherical or flake-like structure. Various techniques were employed to establish the correlation between the structure, crystallibity and surface properties of material. The photocatalyitc performance of material was evaluated by using methyl orange (MO) and phenol as model pollutants in water. The results showed that the flake-like TiO2/GF exhibited the best photocatalytic activity thanks to the improved capability to generate radicals in the material. GF showed helical or plate structures under acid or alkali condition, which facilitated the anchoring of TiO2 on fibre surface and endowed the composites excellent recyclability. 2.Three-dimensional TiO2/graphene composites: To meet the demand for efficiently separating photon-generated carriers and improving the quantum efficiency of TiO2, three-dimensional TiO2/graphene composites were prepard using graphite oxide (GO) and titanium glycolate (TG) as precursors for graphene and TiO2, respectively. The composites exhibited interpenetrated structures of spherical TiO2 nanosphere among the graphene layers with continuois conducting networks. The evaluation on the photocatalysis and photocurrent performances of composites showed that the material had capability to separate photo-induced hole-electron pairs, yielding more free radicals during the photocatalytic reaction. 3.Core-shell structured TiO2@polyaniline (PANI) photocatalyst: To make full use of solar energy, core-shell structured TiO2@PANI composites with strong response to visible light were synthesized using π-conjugated PANI as photosensitizer. The controlled shell on TiO2 effectively prevented the aggregation of nanoparticles and sensitized the core spherical particles. TiO2@PANI composites had large surface area and porous structure, and exhibited enhanced photocatalysis to MO under the visible light, thanks to the capability of material to separate the hole and electrons generated during the photocatalytic reactions. 4.Fibre-based plasmonic photocatalyst: Photocatalyst consisting of nano-scale Ag-AgBr, sub-micro TiO2 and micro-scale GF was prepared, aiming at enhancing the photocatalytic capability of TiO2 using visible light and stabilizing this property under the cyclic runs. The results showed that Ag-AgBr nanoparticles were highly dispersed on the surface of spherical TiO2/GF. The photocatalytic activities of photocatalyst were measured by degrading MO under the visible light (λ ≥ 420 nm). The rate constant for MO degradation was 0.024 min-1, much higher than noble-metal doped TiO2 (0.0037-0.018 min-1) and commercial P-25 (0.0028-0.015 min-1, UV light). The removal

文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4266
专题环境科学与技术研究室
作者单位中国科学院新疆理化技术研究所
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陈琳. 二氧化钛杂化材料的设计、制备及其光催化性能研究[D]. 北京. 中国科学院大学,2015.
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