【作者】 张明义；

【导师】 邵长路；

【作者基本信息】 东北师范大学 ， 材料物理与化学， 2013， 博士

【摘要】 由于光催化技术可以将太阳光能转化为电能和化学能，因此在杀菌、环境净化、光催化、光解水制氢和染料敏化太阳能电池等领域有广泛的应用前景。但光催化技术发展至今仍然存在以下几个主要问题，第一，以二氧化钛为代表的紫外光驱动的光催化剂的量子效率低。第二，光生电子空穴对复合过快。第三，光催化剂难于分离回收。因而，寻求高活性、易回收的可见光光催化剂是解决光催化技术应用的当务之急。本文基于催化剂发展中存在的问题，利用电纺技术结合溶剂热、水热法、原位还原、离子交换等方法制备具有高效可见光催化活性的铋系一维复合纳米光催化剂，通过对异质结型光催化剂的组成和形貌控制试图解决催化剂在应用中的问题。具体内容如下：（1）利用静电纺丝技术和溶剂热方法制备了Bi₂MoO₆微米管材料。首先，以电纺聚丙烯腈（PAN）为模板，通过乙二醇溶剂热方法制备了核壳结构的聚丙烯腈/Bi₂MoO₆（PAN/BMO）混合纤维。然后，通过煅烧去掉PAN/BMO混合微纤维中的电纺PAN获得Bi₂MoO₆微米管（BMO-MTs）。这种BMO-MTs在可见光照射下对于罗丹明B（RB）的降解表现出高的活性。增强的光催化活性可能由于特殊的中空管状结构对光的高利用率和大的比表面积。由于BMO-MTs的大的长径比，它在光催化反应液中能通过沉淀而回收再利用。通过该方法还可以制备其他的铋系复合氧化物微米管，例如Bi₂WO₆和BiVO₄微米管。另外，采用水热方法和原位还原手段对所制备的BiVO₄微管进行进一步的修饰，获得了BVO₄@C/Ag复合微米管材料体系。在可见光的作用下，利用所获得的复合材料降解展示了优于未经修饰BiVO₄微米管的光催化活性。这可归因于该材料的一维中空结构三元组分的光协同作用，导致了高的光利用率和高的量子产率。另外，由于碳层对嵌入其中的Ag纳米粒子起到了保护作用，使Ag纳米粒子不易被氧化，从而保证了光催化剂的稳定性。（2）利用静电纺丝技术和溶剂热方法制备了Bi₂MoO₆/TiO₂纳米纤维异质结材料。在溶剂热反应过程中，通过调控反应浓度，在纳米纤维上分别构造了不同形貌的Bi₂MoO₆次级结构。在该体系中，Bi₂MoO₆可以增加复合体系对可见光的吸收能力，而Bi₂MoO₆和TiO₂所形成的异质结界面则有利于光生电子空穴对的有效分离，因此，在可见光照射下，该异质结构在光催化降解罗丹明B的过程中展现了很好的光催化活性。此外，由于电纺TiO₂纳米纤维所具有的网毡结构，使该材料具有较好的沉降可回收再利用的性质。（3）利用静电纺丝技术和溶剂热方法制备了Bi₂MoO₆/碳纳米纤维异质结材料。可见光催化降解罗丹明B研究表明，Bi₂MoO₆/碳纳米纤维异质结材料具有优于同摩尔比例机械混的Bi₂MoO₆与碳纳米纤维混合物的光催化活性。在该材料体系中，碳纳米纤维优异的导电性能可以使光生电子空穴对的分离效率得到增强，从而使该材料表现出优异的光催化性能。此外，Bi₂MoO₆/碳纳米纤维异质结材料的一维纳米网毡结构，也使其具有优异的可分离及重复使用特性。最后，我们对溶剂热过程中的各种实验参数进行了系统的调控，进而得到了多种Bi₂MoO₆/碳纳米纤维异质结材料，并研究了Bi₂MoO₆次级结构对其的光催化性质的影响。（4）利用静电纺丝技术和溶剂热方法制备了BiOCl/碳纳米纤维异质结材料。在溶剂热反应过程中，通过调控反应浓度，在纳米纤维上分别构造了不同形貌的BiOCl次级结构。紫外光催化降解罗丹明4-硝基酚研究表明，BiOCl//碳纳米纤维异质结材料具有优于单组份BiOCl纳米粉体的光催化活性。在该材料体系中，碳纳米纤维优异的导电性能可以使光生电子空穴对的分离效率得到增强，从而使该材料表现出优异的光催化性能。此外，通过相同的方法，我们制备出了具有可见光催化活性的BiOBr/碳纳米纤维及BiOI/碳纳米纤维异质结材料。（5）对制得的BiOBr/CNFs异质结通过粒子交换技术处理，制备了具有特殊结构的AgBr/BiOBr/碳纳米纤维三元异质结材料。可见光催化降解罗丹明甲基橙（MO）研究表明，AgBr/BiOBr/碳纳米纤维异质结材料具有优于BiOBr/碳纳米纤维异质的二元光催化活性。对光催化机理的研究发现，三元异质结构是加快光生电子空穴对分离的主要原因。更多还原

【Abstract】 It is possible to converse the low density solar energy to chemistry and electricity energy bythe photocatalytic technologies, which provide great potential for the applications insterilization,remediation of environment, H2production by water splitting and dye-sensitizedsolar cell,and so on. However, the photocatalytic technologies still have at least twodisadvantages. First, most of these applications suffer from its dissatisfactory quantumeffciency. Second, the rapid recombination of photoinduced electrons and holes greatlylowers the quantum efficiency. Therefore, to design and develop highly efficient and easy tobe recovered photocatalyts has become the focus of current research. Generally, highly activephotocatalysts have the features of narrow band gap, high quantum efficiency, large specificsurface area, high stability and can be easy recovered. However, in fact, many programs ofimproving photocatalytic activity are still unable to meet the above points. In this dissertation,we focus on development of bismuth-based heterojunctions as photocatalysts, usinghydrothermal and solvothermal methods to control their composition and morphology. Themain contents were discussed as follows:（1） Bi₂MoO₆microtubes （BMO-MTs） were obtained by a two-step fabrication route. Byusing the electrospun polyacrylonitrile （PAN） microfibers as structure-directing hard templateand through ethylene glycol solvothermal method, polyacrylonitrile/Bi₂MoO₆（PAN/BMO）hybrid microfibers with core–shell structures were prepared. Through heat treatment of theas-prepared PAN/BMO to remove the PAN core, Bi₂MoO₆with tubes-structured wereobtained. Photocatalytic tests show that the BMO-MTs possess a much higher degradationrate of Rhodamine B （RB） than that of Bi₂MoO₆prepared by solid-state reaction andconventional P25. The improved photocatalytic performance could be ascribed to the hollowmulti channelled structure and large surface area. The BMO-MTs could be reclaimed easilyby sedimentation from the photocatalytic reaction solution due to the large length to diameterratio of one-dimensional tubes structures. Moreover, such simple and versatile strategy canprovide a general way to fabricate other tubes structures of Bi（III）-containing oxides, such asBi₂WO₆and BiVO₄microtubes. Carbon-modified BiVO₄microtubes embedded by Agnanoparticles （BVO@C/Ag MTs） were obtained by by a combination of hydrothermaltechnique and ion exchange reaction. The photocatalytic studies revealed that theBVO@C/Ag MTs exhibited the highest photocatalytic activity for photodegradation ofRhodamine B （RB） as compared with the pure BiVO₄MTs, BiVO₄@C MTs under visiblelight irradiation. The high separation efficiency of photogenerated electron–hole pairs basedon the photosynergistic effect among the three components of BiVO₄, carbon, and Ag and the improved visible light utilization from the sensitizing effects of carbon layers both contributeto the enhanced photocatalytic activity. The BVO@C/Ag MTs did not exhibit any significantloss of activity after three cycles of the photodegradation process of RB, which results fromthe fact that the presence of carbon layer could inhibit the oxidized and lost of Ag NPs duringrepeated applications.（2） One-dimensional Bi₂MoO₆/TiO₂hierarchical heterostructures with different secondaryBi₂MoO₆nanostructures grown on primary TiO₂nanofibers have been obtained by acombination of electrospinning and a solvothermal technique. The morphology of thesecondary Bi₂MoO₆nanostructures could be controlled by adjusting precursor concentration,and then two different morphologies of Bi₂MoO₆/TiO₂heterostructures with Bi₂MoO₆nanoparticles and nanosheets were successfully achieved. Photocatalytic tests displayed thatthe Bi₂MoO₆/TiO₂heterostructures possessed a much higher degradation rate of Rhodamine B（RB） than the unmodifed TiO₂nanofibers and Bi₂MoO₆under UV and visible light.Moreover, the heterostructures could be reclaimed easily by sedimentation without a decreaseof the photocatalytic activity.（3） A two-step synthesis route combining an electrospinning technique and solvothermalmethod has been accepted as a straightforward protocol for the exploitation ofBi₂MoO₆/carbon nanofibers （CNFs） hierarchical heterostructures which are composed ofBi₂MoO₆nanosheets on the surface of CNFs. Photocatalytic tests display that theBi₂MoO₆/CNFs heterostructures possess a much higher degradation rate of Rhodamine B（RB） than pure Bi₂MoO₆under visible light. The enhanced photocatalytic activity could beattributed to the extended absorption in the visible light region resulting from the Bi₂MoO₆nanosheets, and the effective separation of photogenerated carriers driven by thephotoinduced potential difference generated at the Bi₂MoO₆/CNFs heterojunction interface.Moreover, the heterostructures could be reclaimed easily by sedimentation without a decreaseof the photocatalytic activity. The morphology of the secondary Bi₂MoO₆nanostructurescould be controlled by adjusting the experimental parameters including precursorconcentration, temperature and solvent during the solvothermal process. As a result, differentmorphologies of Bi₂MoO₆/CNFs heterostructures with Bi₂MoO₆nanosheets, nanoparticles,nanoflowers and nanorods were successfully achieved.（4） A two-step synthesis route combining an electrospinning technique and solvothermalmethod has been accepted as a straightforward protocol for the exploitation of BiOCl/carbonnanofibers （CNFs） hierarchical heterostructures which are composed of BiOCl nanosheets onthe surface of CNFs. Photocatalytic tests display that the BiOCl/CNFs heterostructurespossess a much higher degradation rate of4-nitrophenol （4-NP） than pure BiOCl under UVlight. The enhanced photocatalytic activity could be attributed to the effective separation ofphotogenerated carriers driven by the photoinduced potential difference generated at the BiOCl/CNFs heterojunction interface. Moreover, the heterostructures could be reclaimedeasily by sedimentation without a decrease of the photocatalytic activity. Moreover, suchsimple and versatile strategy can provide a general way to fabricate other BiOX （X=Cl, Br,I）/CNFs heterostructures, such as BiOBr/CNFs and BiOI/CNFs.（5） A novel AgBr/BiOBr/CNFs heterostructures was prepared by a rational in situ ionexchange reaction between BiOBr and AgNO3in ethylene glycol. Photocatalytic tests displaythat the AgBr/BiOBr/CNFs heterostructures possess a much higher degradation rate ofmethyl orange （MO） than BiOBr/CNFs heterostructures under visible light. The enhancedphotocatalytic activity could be attributed to the extended absorption in the visible lightregion resulting from the AgBr and BiOBr nanosheets, and the effective separation ofphotogenerated carriers driven by the photoinduced potential difference generated at theAgBr/BiOBr/CNFs heterojunction interface.更多还原