【作者】 李瑞；

【导师】 杜军； 彭海龙； 公振宇；

【作者基本信息】 南昌大学 ， 化学工程（专业学位）， 2021， 硕士

【摘要】 工业废水中各类有机污染物的肆意排放所造成的水体污染问题持续影响着人类的生态文明发展,而利用便捷的阳极氧化工艺和溶液浸渍法制备出高效能的光催化剂去氧化降解污水被认为是解决这一问题的最有效手段之一。本文采用二次阳极氧化技术,以钛片为基底提供原子钛,以氟化铵的乙二醇溶液作为电解液,通过溶剂水提供氧原子,外加两次外电流作用,以肖特基势垒牢固结合纳米管与金属钛导电基板,制备出TiO₂纳米管阵列。对比了二次氧化技术与传统氧化技术的优势,探究了最优工艺条件以获得较好的微观结构与样貌、最佳的光催化性能和亲水性能,包括温度、电压、电极间距、氟化铵浓度和钛基阳极面积等。为拓宽TiO₂光响应范围,降低光生电子和光生空穴复合率,进一步提高光催化性能,进行BiOCl纳米片-TiO₂纳米管阵列的半导体复合实验,构筑p-n异质结型TiO₂基复合光催化剂。探究了复合材料的光催化机理并观察其物相及形貌,并对其进行了元素及价态分析、比表面积和孔体积分析、稳定性分析等,同时研究了不同Bi³⁺浓度下的复合材料对于甲基橙和酸性大红溶液的光降解性能,并探究了p H值对光催化效率的影响,计算出相应的反应动力学方程等。具体研究结果如下:（1）、高密度多晶的锐钛矿相TiO₂纳米管阵列在钛基底上制备成功。XRD图谱和电镜照片显示在[101]晶面方向晶相含量最高,纳米管管长约7μm,管径在150nm左右,排列规整,结构致密,拥有良好的排列规则与有序性。（2）、二次阳极氧化法相比传统的阳极氧化法,通过在反应阶段增加清洗氧化膜的过程,能够得到结晶度更好、排列更加致密规整的TiO₂纳米管阵列,且反应时间可从10h直接缩短到2h。（3）、利用场致溶解理论解释了TiO₂纳米管阵列的形成及成长机理,即将反应过程分为三个阶段:氧化反应阶段、纳米管形成与成长阶段、生成-溶解平衡阶段。（4）、探究了TiO₂纳米管阵列的最优制备工艺条件。采用控制变量的方法,得出在反应温度为25℃、反应电压为55V、电极间距为2cm、氟化铵浓度为0.1mol/L、钛基阳极面积为5cm×2cm条件下,TiO₂纳米管阵列具有最佳的晶相结构、微观形貌、光催化活性以及亲水性能,在这一阶段的实验中,甲基橙和酸性大红溶液的降解率最大可分别达到88.7%和79.3%,光学接触角最低为6.7°。（5）、通过溶液浸渍法成功地在钛基底上制备出了BiOCl纳米片-TiO₂纳米管阵列复合材料。XRD图谱和电镜图片显示生成了四方相BiOCl纳米片,纳米片直径约50nm,沿[110]晶面方向生长,呈团簇状与纳米管表面直接接触。XPS结果表明了复合材料中Ti⁴⁺和Bi³⁺的存在,证明了BiOCl与TiO₂的共存状态。而氮气吸脱附测试显示复合材料的比表面积和孔体积均获得了较大提升,达到了87.774m²/g和0.559cm³/g。（6）、利用能带理论解释了复合材料的光催化机理。复合材料产生了p-n异质结,使得BiOCl和TiO₂相互接触的界面处形成了耗尽区并产生内置电场,电场改变了界面处的能带并为光生电子与光生空穴的分离提供驱动力,这样带负电的光生电子将由电势更负的BiOCl导带跃迁至TiO₂的导带,而带正电的光生空穴将由电势更正的TiO₂的价带跃迁到BiOCl的价带,这样就避免了光生载流子的复合,大大提升光催化性能。复合材料对甲基橙和酸性大红溶液的降解率最大可达99.1%和97.4%,且在循环三次实验后,依然保持了较高的降解效果。（7）、探究了BiOCl的含量对复合材料性质的影响。在Bi³⁺浓度为0.03mol/L时,四方相BiOCl的结晶度最高,纳米片在与纳米管阵列接触的同时留有空隙,为p-n异质结构建及接受充足的光源提供了条件。在此条件下,复合材料满足一级反应动力学方程,拥有最大降解速率的同时,保持了最佳的降解率。（8）、探究了复合材料在不同p H环境下的降解效果。结论为在p H值为6时,复合材料能够发挥最佳的光催化性能。更多还原

【Abstract】 The water pollution problem caused by the indiscriminate discharge of various organic pollutants continues to affect the development of human ecological civilization.It is considered to be one of the most effective ways to solve this problem that the high efficient photocatalyst is prepared by convenient anodizing process and impregnation method to oxidize and degrade wastewater.In this dissertation,the secondary anodization technology is adopted,and the titanium sheet is used as the substrate to provide atomic titanium,the ammonium fluoride glycol solution is as the electrolyte,and oxygen atoms are provided by the solvent water.Through the action of two external currents,the nanotubes and the metal titanium conductive substrate are firmly combined with the Schottky barrier,thus TiO₂ nanotube arrays are prepared.The differences of secondary oxidation technology and traditional oxidation technology are compared,and the optimal process conditions,including temperature,voltage,electrod gap,NH₄F concentrations and the areas of titanium-based anodes,are explored to obtain better microstructure,appearance,photocatalytic and hydrophilic performance.In order to broaden the photoresponse range of TiO₂,reduce the recombination rate of photo-generated electrons and photo-generated holes,and further improve the photocatalytic performance,a semiconductor composite experiment of BiOCl nanosheets-TiO₂ nanotube arrays is carried out,we want to construct a p-n heterojunction TiO₂-based composite photocatalyst.The photocatalytic mechanism of the composites is explored and the phase and morphology,the element and valence state,specific surface area and pore volume,stability are analyzed.At the same time,the photodegradation performance of the composites with different Bi³⁺concentrations on methyl orange and acid red solutions are studied,the effect of p H on the photocatalytic efficiency and reaction kinetic equations are explored.The specific research results are as follows.（1）High-density polycrystalline anatase phase TiO₂ nanotube arrays are successfully prepared on a titanium substrate.XRD and electron microscope photos show that the crystal phase content is highest along the[101]crystal plane direction,the tube length is about 7μm,and the diameter is about 150nm.The arrangement is regular and the structure is dense,it has great arrangement rules and order.（2）Compared with the traditional anodic oxidation method,the secondary can obtain TiO₂ nanotube arrays with higher purity,better crystallinity,and a more regular arrangement through the process of cleaning the oxide film in the reaction stage,and the reaction time can be directly shortened from 10 h to 2 h.（3）The field-enhanced dissolution theory is used to explain the formation and growth mechanism of TiO₂ nanotube arrays.The reaction process is divided into three stages:oxidation reaction stage,nanotube formation and growth stage,and formation-dissolution equilibrium stage.（4）The optimal preparation process conditions of TiO₂ nanotube arrays are explored.Using the method of controlling variables,it is concluded that under the conditions of 25°C,55V,2cm electrod gap,0.1mol/L NH₄F concentrations and5cm×2cm areas of titanium-based anodes,TiO₂ nanotube arrays exhibit the best crystal phase structure,microscopic morphology,photocatalytic activity and hydrophilic properties.The degradation rates of methyl orange and acid red solutions reach 88.7%and 79.3%,respectively,and the lowest optical contact angle is 6.7°.（5）The BiOCl nanosheet-TiO₂ nanotube arrays composite is successfully prepared on the titanium substrate by impregnation method.XRD patterns and electron microscopy pictures show that tetragonal BiOCl nanosheets are generated,and the nanosheets are about 50nm in diameter,grow along the（110）crystal plane,and they are in clusters that contact directly with the surface of the nanotubes.XPS results show the existence of Ti⁴⁺and Bi³⁺in the composite and prove the coexistence state of BiOCl and TiO₂.The nitrogen absorption and desorption test show that the specific surface area and pore volume of the composite have been greatly improved,reaching87.774m²/g and 0.559cm³/g.（6）The energy band theory is used to explain the photocatalytic mechanism of composite.The composite produces p-n heterojunction which makes the depletion zone,and internal electric field formed at the interface where BiOCl and TiO₂ contact each other,which changes the energy band at the interface and provides a driving force for the separation of photogenerated electrons and photogenerated holes.In this way,the negatively charged photogenerated electrons will transfer from the more negative BiOCl conduction band to the conduction band of TiO₂,and the positive charged photo-generated holes will transfer from the valence band of TiO₂ with more positive potential to the valence band of BiOCl,thus the recombinations of photo-generated carriers are avoided and the photocatalytic performance is greatly improved.（7）The influence of BiOCl content on composite is explored.When the Bi³⁺concentration is 0.03mol/L,the tetragonal BiOCl has the highest crystallinity,and the nanosheets are in contact with the nanotube array while leaving gaps,which provides conditions for building p-n heterojunction and receiving sufficient light sources.Under this condition,the composite meets the first-order reaction kinetics equation and has the maximum degradation rate while maintaining the best degradation rate.（8）The degradation effect of composite under different p H environments is explored,the conclusion is that when the p H value is 6,the composite can exert the best photocatalytic performance.更多还原