【作者】 贾志方；

【导师】 张宝泉； 王富民；

【作者基本信息】 天津大学 ， 工业催化， 2011， 博士

【摘要】 最近几年来,利用新型高效的可见光催化剂处理环境污染问题已经成为重点研究内容之一。本文采用水热法合成了一系列可见光响应催化剂:Zn_xCd_1-xS、铋系光催化剂（Bi₂MoO₆,BiOX（X=Br, I））以及InVO₄。同时,利用XRD、SEM、TEM、UV-vis DRS以及N₂吸附-脱附等手段对它们的结构、形貌、光催化活性以及光催化机理进行了研究。具体工作如下:1.采用低温水热法合成了一系列由纳米颗粒组成的单分散球状Zn_xCd_1-xS,随着Cd含量的增加,Zn_xCd_1-xS的价带位置向更负的方向移动,而导带则向更正的方向移动,其中Zn_0.4Cd_0.6S光催化效果最佳,根据Zn_xCd_1-xS固溶体的价带和导带信息,我们推测hVB⁺、·OH、HO_<sup>2·、O_2·^-是参与Zn_xCd_1-xS降解RhB反应的主要活性氧化物种。此外,采用溶剂热法制备了Zn_xCd_1-xS固溶体,发现随着Zn/Cd摩尔比的减小,产物的形貌由六面体逐渐转变为纳米棒状。2.采用柠檬酸（CA）辅助水热法合成了尺寸可控的Bi₂MoO₆纳米片,并且对CA辅助水热合成纳米片的机理进行了探讨。此外,我们还探讨了前驱液pH值对光催化活性的影响,结果表明,pH为3.08时的Bi₂MoO₆活性最高。3.用PVP作为表面修饰剂,通过低温水热法合成了多层花状的BiOX（X=Br,I）。该花状结构由纳米片组装而成,PVP对这种结构的形成起了重要的作用。研究发现形貌对BiOBr的光催化性能有明显影响,由于花状BiOBr具有更高的比表面积,其光催化性能明显优于纳米片状的BiOBr4.采用溶剂热法合成了三维BiOBr_xI_1-x微米球,微米球是由二维纳米片组装而成的。Br/I摩尔比例对产物的BET表面积、孔结构、价带水平以及带隙值均有较大影响,相应的光催化活性也有较大差别,其中BiOBr_0.2I_0.8光催化性能最优,这可能是高比表面积、多孔结构、以及光吸收的增强三者之间共同协调作用的结果。最后,根据对价带和导带的分析,我们推测hVB⁺是参与BiOBr_xI_1-x降解RhB反应的主要活性氧化物种。5.采用水热法合成了InVO₄光催化剂,并通过浸渍法制备了Fe₂O₃/InVO₄、NiO/InVO₄、CuO/InVO₄,光催化还原CO₂实验表明,反应产物主要为甲醇,Fe₂O₃/InVO₄活性最高,反应8小时后甲醇浓度达到191.45ppm。当Fe₂O₃与InVO₄复合时,由于它们具有合适的能带位置,从InVO₄上激发出来的电子能够转移到Fe₂O₃的导带上,从Fe₂O₃上激发出来的空穴能够转移到InVO₄的价带上,使电子-空穴对能够有效分离,从而提高其还原CO₂生成甲醇的能力。更多还原

【Abstract】 In recent years, application of novel, efficient visible-light induced photocatalysts on solving environmental issues has become one of the most important research areas. In this work, several kinds of visible-light induced photocatalysts, Zn_xCd_1-xS, photocatalysts containing bismuth such as Bi₂MoO₆ and BiOX（X=Br, I） and InVO₄ were synthesized by hydrothermal method or solvothermal method. The prepared samples were characterized by XRD, SEM, TEM, UV-vis DRS, and nitrogen sorption/desorption to investigate the structure, morphology, photocatalytic activity and the photocatalytic mechanism of photocatalysts. The detailed works were summarized as follows.1. A series of monodisperse Zn_xCd_1-xS spheres composed of nanoparticles have been successfully fabricated in high yield by a facile hydrothermal route at a relatively low temperature. The positions of conduction band and valence band for the solid solution of Zn_xCd_1-xS were shifted toward more positive potential and more negative potential with the increase of Cd content, respectively. Among all the prepared samples, Zn_0.4Cd_0.6S exhibited the best photocatayltic activity. According to the information of the valence band and conduction band, the hVB⁺,·OH, HO_<sup>2·, and O_2·^- are regarded as the main active species during the photodegradation of RhB. In addition, we have also synthesized the Zn_xCd_1-xS solid solution via a simple one-pot solvothermal method. It was found that the morphologies of the products show a gradient evolution from hexagon to nanorods with decreasing the molar ratio of Zn/Cd.2. Bi₂MoO₆ nanoplates with different sizes have been controllably fabricated by citric acid （CA） assisted hydrothermal process and the mechanism for CA assisted hydrothermal synthesis of the Bi₂MoO₆ nanoplates is discussed. Moreover, the effect of pH values of the precursors on photocatayltic activity was investigated, the best photocatayltic activity was obtained at pH=3.08.3. Using polyvinylpyrrolidone （PVP） as surface modifier, we present a facile, one-step hydrothermal method for fabricating multilayered flower-like BiOX（X=Br, I） at a relatively low temperature of 120°C. Such three-dimensional （3D） BiOBr assemblies were constructed layer-by-layer from a large number of two-dimensional （2D） nanoplates and PVP plays an important role in the formation of flower-like structure. The morphology of the BiOBr sample can influence significantly on the photocatalytic properties, the BiOBr flowers exhibited higher visible-light photocatalytic activity than that of irregular BiOBr nanoplates due to its higher surface area.4. Self-assembled 3D BiOBr_xI_1-x microspheres composed of nanoplates have been successfully synthesized by a facile solvothermal method.The variation of molar ratio of Br/I leads to changes in their BET surface areas, porous structure, level of valence band and light absorption ability associated with the changes in band gap. It is shown that changes in optical and structural characteristics of BiOBr_xI_1-x solid solutions influence photocatalytic activity. Among all the prepared samples, the as-synthesized BiOBr_0.2I_0.8 microspheres possessed the best photocatalytic activity under visible light irradiation, which is ascribed to their energy band structure, high BET surface area, and porous structure. In addition, the photoinduced holes （hVB⁺） are regarded as the main active species during the photodegradation process based on analysis of the valence band and conduction band.5. InVO₄ was synthesized by hydrothermal method. Fe₂O₃/InVO₄, NiO/InVO₄ and CuO/InVO₄ were synthesized by impregnation method. The photocatalytic reduction of CO₂ experiments showed that the main production was methanol, Fe₂O₃/InVO₄ had the highest photocatalytic activity and the methanol concentration reached 191.45ppm after 8 hours’reaction. Fe₂O₃ and InVO₄ have matching band potentials, photoinduced electrons on the InVO₄ conduction band can transfer to the Fe₂O₃ conduction band, photoinduced holes Fe₂O₃ valence band can transfer to the InVO₄ valence band, which can promote the effective separation of photoinduced electron-hole pairs and enhace the ability to photoreduction CO₂ to yield methanol.更多还原