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苝酰亚胺基有机半导体及其复合物的可见光催化分解水制氢性能研究
陈帅
学位类型博士
导师王传义
2015-05-28
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
关键词氢能 半导体光催化 光催化剂 苝二酰亚胺 自组装
摘要

氢气兼具高燃烧值和无污染两大优势,是理想的绿色清洁能源。目前工业化的制氢途径主要包括化石能源裂解和水的电解,存在成本高、耗能多和污染大等缺陷。直接利用取之不竭的太阳能光催化分解水制取氢气是一种兼顾能耗、资源和环境的,最为理想、最有前途和最安全的氢能开发技术。此技术实用化的关键和核心在于开发高效的可响应可见光的半导体光催化剂,此类光催化剂材料的开发也是限制该技术实用化的瓶颈。鉴于半导体光催化剂的发展现状,结合材料科学和纳米科技的发展前沿,本论文将n型有机半导体苝酰亚胺基分子(选择苝二酰亚胺衍生物为研究对象)及其超分子自组装的概念和方法引入光催化领域,构建了一系列新型的复合半导体光催化材料体系,系统研究了该系列光催化剂在可见光催化分解水制氢方面的性能,为半导体光解水制氢材料的发展提供了新的思路、实验依据和理论支持。本论文主要开展了如下几个方面的研究工作:1、设计并采用简单高效的合成路线制备了一系列酰胺位取代的苝二酰亚胺衍生物(PTCDIs)分子,包括对称取代的分子:N,N'-双十二烷基- PTCDI、N,N'-双(二甲基胺基-p-苯基)-PTCDI、N,N'-双(二甲基胺基-p-苄基)- PTCDI,和非对称取代的分子:N-十二烷基-N'-(二甲基胺基-p-苯基)- PTCDI、N-十二烷基-N'-(二甲基胺基-p-苄基)-PTCDI。其中,十二烷基的修饰有助于改善PTCDIs分子的溶解性,利于其进行超分子自组装;二甲基胺基-p-苯基和二甲基胺基-p-苄基均为富电子基团,用于和缺电子的PTCDI环骨架构成电子给体-电子受体型分子结构。2、采用简单的双溶剂相转移自组装策略,以三氯甲烷为良溶剂,甲醇为不良溶剂,研究了所制备的PTCDIs分子的自组装性能,探讨并对比了不同取代基对自组装行为及最终获得的聚集体形貌的影响,成功制备了一系列PTCDIs一维纳米纤维,其中十二烷基侧链修饰的分子具有规整的纤维形貌和更长程有序的纳米结构。这些PTCDIs纳米纤维具有热力学稳定的一维有序堆叠结构,可以从溶剂相转移至固体材料表面。3、通过与助催化剂铂(Pt)、二氧化钛(TiO2)、或石墨相氮化碳(g- C3N4)复合,成功构建了一系列新型的基于PTCDIs一维纳米纤维或聚集体的复合半导体材料,主要包括Pt/PTCDIs纳米纤维、Pt/TiO2/PTCDIs纳米纤维、PTCDIs(聚集体)/Pt/P25、PTCDIs(聚集体)/Pt/g-C3N4。其中,Pt均采用简单的紫外光还原方法原位负载在半导体材料表面;TiO2采用简单的有机钛源原位水解的方法负载在PTCDIs纳米纤维的表面;P25为德固赛(Degussa)气相法纳米TiO2产品;PTCDIs一维纳米纤维是采用双溶剂界面组装的方法获得,类似的手段也用于将PTCDIs聚集体与Pt/P25或Pt/g-C3N4的复合。该系列PTCDIs复合半导体光催化材料具有良好的光化学稳定性,与TiO2和g-C3N4相比,具有更好的可见光响应性能。4、在可见光(波长≥ 420 nm)的激发下,以含牺牲试剂甲醇或三乙醇胺的水溶液为反应体系,研究了上述复合材料作为光催化剂的光解水制氢性能。6小时内,Pt/PTCDIs纳米纤维的平均产氢速率可达0.035 μmol h-1,PTCDIs/Pt/P25的平均产氢速率可达0.075 μmol h-1,Pt/TiO2/PTCDIs一维纳米纤维的平均产氢速率可达0.125 μmol h-1,相对比,PTCDIs一维纳米纤维本身和Pt/P25几乎不具有可见光光解水制氢活性;PTCDIs/Pt/g-C3N4作为光催化剂平均产氢速率可高达0.375 μmol h-1,是Pt/g-C3N4光催化剂速率的10倍左右。有机半导体分子PTCDIs的电子给体-受体结构、π-π堆叠自组装及一维纳米纤维形貌、合适的匹配能级、良好的可见光响应性能、优异的光化学和热学稳定性等性能,对于以上复合半导体光催化剂在可见光催化分解水制氢的应用中起到关键的作用。

其他摘要
Hydrogen (H2) is an ideal green energy source to alleviate the impact of fossil fuel scarcity and environmental risk because it is renewable, energy dense, and environmentally friendly. Splitting water using a photocatalytic reduction reaction on the semiconductor surface utilizing abundant solar energy has been demonstrated as a promising approach for clean, cost-effective production of hydrogen. The key of this technique is the discovery of high efficient visible-light-driven semiconductor photocatalysts, which still faces much challenge and is far from real commercialization. To meet these challenges, our efforts have been put into the design and development of new photocatalyst materials (or composites). In this thesis, a series of semiconductor composites base on a kind of air-stable n-type organic semiconductor, perylene tetracarboxylic diimides, have been fabricated and utilized for photocatalytic water splitting reaction to produce hydrogen. The supramolecular self-assembly concepts and methods of perylene tetracarboxylic diimides have been introduced into this field, providing novel insight into this field. The research covers several main aspects as following: 1. A series of perylene tetracarboxylic diimide (PTCDI) molecules have been designed and synthesized via facile and efficient reaction routes. Based on the side-chain modification, these molecules can be divided into both symmetric PTCDI molecules: N,N'-didodecyl-PTCDI, N,N'-di(4-(dimethylamino)phenyl)-PTCDI and N,N'-di(4-(dimethylamino)benzyl)-PTCDI, and asymmetric molecules: N-dodecyl-N'-(4-(dimethylamino)phenyl)-PTCDI and N-dodecyl-N'-(4-(dimethylamino)benzyl)-PTCDI. Herein, the modification of dodecyl group has been used to improve the solubility of PTCDI molecules which is good for their supramolecular self-assembly in solution phase. The electron-rich moieties, 4-(dimethylamino)phenyl and 4-(dimethylamino)benzyl groups can be in combination with electron-deficient PTCDI cores to form electron donor-acceptor type molecular structures of PTCDI molecules. 2. The self-assembly behavior of PTCDI molecules has been studied through facile bisolvent phase-transfer methods using chloroform as the “good” solvent and methanol as the “poor” solvent. The effect of dodecyl and/or phenylamino group modification on the nanofibil morphology of PTCDIs, intramolecular charge transfer behaviour and the photocatalytic performance of PTCDI-based composites has been discussed. Different form the side-group modification, a series one-dimensional (1D) nanofibers of PTCDIs have been fabricated. These 1D nanofibers possess thermodynamic stable π-π stacking morphologies and can be transferred from the solutions to the surfaces of solid substrates without disrupting their structures. 3. A series of novel nanocomposite structures have been fabricated by in-situ deposition of TiO2 layers and/or a co-catalyst (Pt) on 1D self-assembled nanofibers of PTCDIs, or employing molecular aggregates of PTCDI bearing electron-rich phenylamino or benylamino moiety as a sensitizer to combine with Pt/TiO2 nanoparticles (Degussa P25) or Pt/g-C3N4 via solution processing. These composites thus fabricated exhibit broader visible-light response than TiO2 or g-C3N4, and possess excellent photochemical stability. 4. Under visible-light irradiation ((λ≥ 420 nm), hydrogen production for all composite systems has been explored through photocatalytic water splitting in aqueous solutions with sacrificial electron donor methanol or triethanolamine, proving the applicability of PTCDI organic semiconductors in photocatalytic system. When 25 mg of the composite powders were suspended into aqueous solution, stable hydrogen evolution with the highest activity of ~0.035 μmol h-1 has been achieved for Pt/PTCDI nanofibers, ~0.075 μmol h-1 for PTCDI/Pt/P25, ~0.125 μmol h-1 for Pt/TiO2/PTCDI nanofibers, ~0.0375 μmol h-1 for PTCDI/Pt/g-C3N4 which is about tenfold higher than that of Pt/g-C3N4. In comparison, Pt/PTCDI nanofibers and Pt/TiO2 nanoparticles are nearly ineffective under the same photocatalytic reaction conditions. Compared to the well-defined nanofibil morphology obtained from dodecyl-substituted PTCDI molecules, donor-accepter type PTCDIs attached with electron-rich phenylamino moieties show much improved photocatalytic activity due to efficient inter- and intra-molecular charge transfer. The initial intramolecular charge transfer of PTCDI and its energy level being well matched to TiO2 or g-C3N4, strong visible-light response, excellent photochemical stability, and nanofibril morphology have been found to be the key to the effective visible-light photoactivity of PTCDI assemblies.
文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4234
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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陈帅. 苝酰亚胺基有机半导体及其复合物的可见光催化分解水制氢性能研究[D]. 北京. 中国科学院大学,2015.
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