卤氧化铋光催化材料的制备及性能调控

发布时间：2018-06-11 21:14

本文选题：溴氧化铋 + 暴露面积　；参考：《江南大学》2016年硕士论文

【摘要】：21世纪以来,我国环境问题十分严峻,各种环境污染事件层出不穷,且损害程度越来越大。光催化氧化技术作为一种新型的环境友好型治理技术由于具有明显的节能、高效、稳定、无二次污染等多重优势,吸引了大众的目光。虽然在过去很长时间里,大量的研究都集中在开发和优化新型光催化材料上,但是大部分光催化材料仍然存在活性晶面暴露面积小,光吸收范围窄及电子-空穴分离效率低等弊端,从而限制了它的广泛应用。卤氧化铋光催化材料因其可调节的层状结构,并且具有从紫外光到可见光优异的光吸收能力,研究价值很高。本文致力于合成出高效的卤氧化铋光催化材料,同时对其进行光催化性能研究,并以提高单位体积活性晶面暴露面积,构筑少层固溶体结构和原位还原Bi形成Bi/BiOI复合光催化剂三种不同方式来调控卤氧化铋光催化活性。具体内容如下:1.采用溶剂热法合成了一系列不同尺寸的BiOBr纳米片样品。以罗丹明B,甲基橙和苯酚为目标降解物,在可见光照射下,研究了BiOBr光催化剂{001}晶面暴露比和尺寸对性能的影响规律,结果表明,具有相似{001}晶面暴露比、不同尺寸的BiOBr纳米片表现出不同的光催化性能,尺寸小的BiOBr表现出更加高效的光催化性能。并且长度和厚度方向上的尺寸对光催化性能有不同的影响,厚度对光催化性能的影响大于长度对光催化性能的影响。此外,通过分析厚度与单位体积{001}晶面暴露面积、以及单位体积{001}晶面暴露面积和{001}晶面暴露比之间的关系,得出厚度影响光催化性能的本质原因是厚度可以改变参与光催化反应的BiOBr纳米片单位体积暴露的活性{001}晶面面积大小,并且单位体积{001}晶面暴露面积在0.022 nm-1到0.111 nm-1的范围内,与光催化降解速率常数k呈现良好的线性关系。因此,BiOBr纳米片的光催化性能是由单位体积暴露的活性{001}晶面面积而不是{001}晶面暴露比来控制的。2.利用单位体积活性晶面暴露面积和特殊固溶体结构对光催化性能的协同作用,采用溶剂热法制备了少层BiOClxBr1-x固溶体纳米结构。通过对BiOClxBr1-x的物相和形貌表征,确定所合成的样品是少层固溶体BiOClxBr1-x纳米结构,而非BiOCl和BiOBr复合物,同时得出所合成的固溶体纳米片的厚度在6 nm以内,且高度暴露{001}晶面。通过对一系列不同比例的BiOClxBr1-x固溶体进行带隙和价带顶位置分析,发现随着x值的增加,固溶体带隙值逐渐增加,价带顶位置逐渐升高,表明BiOClxBr1-x固溶体带隙和价带顶位置具有可调节性。在可见光照射下,以罗丹明B和甲基橙为降解对象,发现当x=0.4时,BiOCl0.4Br0.6表现出最佳的光催化性能。此外,通过对比不同厚度BiOCl0.4Br0.6固溶体对罗丹明B和甲基橙的降解性能,发现片层薄的少层BiOCl0.4Br0.6固溶体光催化性能明显优于片层较厚的BiOCl0.4Br0.6固溶体。3.以Bi(NO_3)_3·5H_2O作为铋源,Na I为碘源,小分子葡萄糖为还原剂,蒸馏水为溶剂,水热法原位还原铋离子得到Bi/BiOI复合光催化剂。通过对所合成的复合光催化剂的物相、形貌和光学性质进行研究,得出所合成的复合光催化剂为片层状结构,金属Bi是以颗粒的形式负载在BiOI纳米片上,且Bi/BiOI复合光催化剂的最佳合成温度为160 oC,反应时间6 h,葡萄糖的用量为0.8 g。以罗丹明B为降解对象,对所制备样品在可见光下的光催化活性进行评价,并考察了水热反应温度、反应时间及葡萄糖用量对所制备的Bi/BiOI光催化性能的影响。研究结果表明,当反应温度为160 oC,反应时间6 h,葡萄糖的用量为0.8 g,Bi/BiOI复合光催化剂的光催化性能最佳。
[Abstract]:Since twenty-first Century, environmental problems in China are very severe, and all kinds of environmental pollution events emerge in endlessly, and the degree of damage is increasing. As a new environmental friendly treatment technology, photocatalytic oxidation technology has attracted the public's attention because of its obvious advantages of energy saving, high efficiency, stability and no two pollution. In time, a large number of studies have focused on the development and optimization of new photocatalytic materials, but most of the photocatalytic materials still have the disadvantages of small exposure area of active crystal surface, narrow light absorption range and low electron hole separation efficiency, thus limiting its wide application. And with excellent light absorption capacity from ultraviolet to visible light, the research value is very high. This paper is devoted to the synthesis of high efficient bismuth halide photocatalytic materials, at the same time to study the photocatalytic properties of the photocatalyst, and to improve the surface area of the unit volume active crystal surface, to construct the structure of small solid solution and to form the in situ reduction of Bi to form Bi/BiOI composite light The photocatalytic activity of bismuth halide is regulated in three different ways. The specific content is as follows: 1. a series of BiOBr nanoscale samples with different sizes are synthesized by solvent heat method. The target degradation products are Luo Danming B, methyl orange and phenol, and the exposure ratio of BiOBr photochemical agent {001} surface and the effect of size on the properties are studied under visible light. The results show that the BiOBr nanometers with similar {001} surface exposure ratio have different photocatalytic properties, and the smaller size BiOBr shows more efficient photocatalytic performance. And the size of the length and thickness direction has different effects on the photocatalytic performance, and the thickness has more influence on the photocatalytic performance than the length. In addition, the relationship between the exposure area of the thickness and unit volume of {001} crystal surface, and the relationship between the exposure area of the unit volume {001} crystal surface and the {001} surface exposure ratio are analyzed. The essential reason that the thickness affects the photocatalytic performance is that the thickness can change the unit volume exposure of the BiOBr nanometers involved in the photocatalytic reaction. The size of the active {001} surface area, and the exposure area of the unit volume {001} crystal surface from 0.022 nm-1 to 0.111 nm-1, has a good linear relationship with the photocatalytic degradation rate constant K. Therefore, the photocatalytic performance of the BiOBr nanoscale is controlled by the active {001} surface area exposed by unit volume rather than the exposure ratio of the {001} surface. .2. uses the synergistic effect of the unit volume active crystal surface area and the special solid solution structure on the photocatalytic performance. The solvothermal method is used to prepare the nanoscale BiOClxBr1-x solid solution nanostructures. By characterization of the phase and morphology of BiOClxBr1-x, the synthesized samples are small layers of solid solution BiOClxBr1-x nanostructures, not BiOCl and Bi. At the same time, the OBr composite was found to be less than 6 nm and highly exposed to the {001} crystal surface. Through the analysis of the band gap and the position of the valence band top of a series of different BiOClxBr1-x solid solutions, it was found that the band gap value of the solid solution increased gradually with the increase of x value, and the position of the valence band increased gradually, indicating BiOClxBr1-x. The band gap of solid solution and the position of valence band top are adjustable. Under visible light, rhodamine B and methyl orange are degraded. When x=0.4, BiOCl0.4Br0.6 shows the best photocatalytic performance. In addition, by comparing the degradation properties of BiOCl0.4Br0.6 solid solution of different thickness to rhodamine B and methyl orange, the thin layer of thin layer B is found. The photocatalytic performance of iOCl0.4Br0.6 solid solution is better than that of thick BiOCl0.4Br0.6 solid solution.3. with Bi (NO_3) _3. 5H_2O as a bismuth source, Na I as iodine source, small molecule glucose as reducing agent, distilled water as solvent, and in situ reduction of bismuth ions by hydrothermal method to obtain Bi/BiOI compound photocatalyst. The composite photocatalyst synthesized is lamellar structure, and the metal Bi is loaded on BiOI nanoparticles in the form of particles, and the optimum synthesis temperature of the Bi/BiOI composite photocatalyst is 160 oC, the reaction time is 6 h, the dosage of glucose is 0.8 g., and the Luo Danming B is degraded, and the prepared samples are visible. The photocatalytic activity under light was evaluated, and the effects of the reaction temperature, time and amount of glucose on the photocatalytic properties of Bi/BiOI were investigated. The results showed that the photocatalytic performance of the Bi/BiOI complex photocatalyst was the best when the reaction temperature was 160 oC, the reaction time was 6 h, the dosage of glucose was 0.8 g.
【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36

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