钨酸铋基三元复合光催化剂的可控合成及光催化性能研究

发布时间：2019-03-22 15:59

【摘要】：作为新型可见光光催化剂,Bi2WO6被认为是铋系化合物中具有最佳光催化活性的半导体材料之一。尽管通过优化原料和制备工艺来改变Bi2WO6的尺寸和形貌来进一步提高其光催化降解污染物的效果,但光生载流子复合率高、可见光响应范围窄等缺点,还有待于进一步提高。因此,对纯的Bi2WO6进行掺杂、复合、贵金属修饰来改变其组分以进一步提高其可见光光催化活性仍是研究的主流方向。本论文从提高纯的Bi2WO6光催化降解活性这一迫切需要解决的问题出发,采用半导体复合形成异质结的方式,通过复合相的选择和控制Bi2W06基异质结的形貌来解决其在实际应用中存在的问题。相关研究结果如下：(1)以Bi(NO3)3·5H2O作为铋源,Na2WO4·2H2O作为钨源,分别采用水热-煅烧法和一步水热法制备花状WO3/Bi2WO6 n-n型异质结微球。研究了WO3的修饰量对产物结构、形貌、光催化活性等的影响。通过两种方法的对比得知,一步法所制备的花状WO3/Bi2WO6异质结微球的纳米片更薄更密、比表面积更大、可提供更多的活性位点,有利于光的吸收和污染物的吸附,并且制备工艺简单可降低成本,可作为后续形成三元异质结的基体材料。(2)以一步法所制备的花状WO3/Bi2WO6 n-n型异质结微球为基体,通过浸渍-煅烧工艺制备一系列不同CuO含量修饰的CuO-WO3-Bi2WO6p-n-n型双异质结复合体系。UV-vis结果表明随着CuO修饰量的增加,CuO-WO3-Bi2WO6双异质结将Bi2WO6的光吸收范围拓展至近红外区。光催化结果表明CuO-WO3-Bi2WO6三元复合体系的降解效果明显高于纯的Bi2WO6和其他Bi2WO6基二元异质结,并且适量的CuO能使WO3/Bi2WO6降解RhB的效果最佳。(3)采用水热-液相法制备BiOBr-WO3-Bi2WO6层级结构。SEM结果表明BiOBr的复合并没有改变WO3/Bi2WO6异质结的花状超结构,且适量BiOBr均匀的分散在WO3/Bi2WO6花状结构的表面。在可见光的照射下,BiOBr-WO3-Bi2WO6三元层级结构降解RhB的光催化活性明显高于Bi2WO6和WO3/Bi2WO6,这主要归结于花状结构大的比表面积,界面的紧密接触和匹配的能带位置,这些都有利于光生电子-空穴对的有效分离及光催化效果的提高。(4)以WO3/Bi2WO6为基体,采用沉淀法制备出了一系列花状Ag3PO4-WO3-Bi2WO6三元体系在很大程度上提高了VO3/Bi2WO6对可见光的吸收能力。光催化实验表明适量Ag3PO4修饰的WO3/Bi2WO6降解RhB的效果最佳,这是因为适量Ag3PO4纳米颗粒均匀的分散在花状WO3/Bi2WO6微球和纳米片上,并且Ag3PO4-WO3-Bi2WO6三元复合光催化材料中的导带可形成层级结构,电子可从Bi2WO6的导带转移到Ag3PO4,接着转移到WO3的导带,进而有效促进光生载流子的分离。总之,本论文研究了一系列新型花状WO3/Bi2WO6基三元异质结光催化剂,该催化剂有效地提高了WO3/Bi2WO6对可见光的吸收以及量子效率。
[Abstract]:As a new visible photocatalyst, Bi2WO6 is considered to be one of the semiconductor materials with the best photocatalytic activity in bismuth compounds. Although the size and morphology of Bi2WO6 can be further improved by optimizing the raw material and preparation process, the high photogenerated carrier recombination rate and narrow visible light response range need to be further improved. Therefore, doping, recombination and noble metal modification of pure Bi2WO6 to change its components to further improve its visible photocatalytic activity are still the main research direction. In this thesis, to improve the photocatalytic degradation activity of pure Bi2WO6, we adopt the method of semiconductor recombination to form heterojunction, which is an urgent problem to be solved in order to improve the photocatalytic degradation activity of Bi2WO6. The problems existing in the practical application of Bi2W06-based heterojunction are solved by selecting the composite phase and controlling the morphology of the heterojunction. The results are as follows: (1) using Bi (NO3) 3 路5H2O as bismuth source and Na2WO4 路2H2O as tungsten source, flower WO3/Bi2WO6 n-type heterojunction microspheres were prepared by hydrothermal-calcination method and one-step hydrothermal method, respectively. The effects of the modification amount of WO3 on the structure, morphology and photocatalytic activity of the products were studied. Through the comparison of the two methods, it was found that the nanospheres of flower-like WO3/Bi2WO6 heterojunction microspheres prepared by one-step method were thinner and denser, and the specific surface area was larger, which could provide more active sites and facilitate the absorption of light and the adsorption of pollutants. Moreover, the simple preparation process can reduce the cost and can be used as the matrix material for the subsequent formation of ternary heterojunction. (2) the flower-like WO3/Bi2WO6 n-n heterojunction microspheres prepared by one-step method are used as the matrix. A series of CuO-WO3-Bi2WO6p-n- n-type double heterojunction composite systems modified with different CuO content were prepared by impregnation-calcination process. The results of UV-vis showed that with the increase of CuO content, the amount of CuO was increased. CuO-WO3-Bi2WO6 double heterojunction extends the optical absorption range of Bi2WO6 to near infrared region. The photocatalytic results showed that the degradation efficiency of CuO-WO3-Bi2WO6 ternary composite system was significantly higher than that of pure Bi2WO6 and other Bi2WO6-based binary heterojunctions. Moreover, appropriate amount of CuO could make WO3/Bi2WO6 degrade RhB best. (3) BiOBr-WO3-Bi2WO6 hierarchical structure was prepared by hydrothermal-liquid phase method. SEM results showed that the composite of BiOBr did not change the flower-like superstructure of WO3/Bi2WO6 heterojunction. And appropriate amount of BiOBr dispersed evenly on the surface of WO3/Bi2WO6 flower-like structure. Under visible light irradiation, the photocatalytic activity of BiOBr-WO3-Bi2WO6 ternary hierarchy degradation of RhB is obviously higher than that of Bi2WO6 and WO3/Bi2WO6, which is mainly attributed to the large specific surface area of flower-like structure, the close contact of the interface and the matching position of energy band. All of these are beneficial to the effective separation of photogenerated electron-hole pairs and the improvement of photocatalytic efficiency. (4) WO3/Bi2WO6 as the matrix. A series of flowered Ag3PO4-WO3-Bi2WO6 ternary systems were prepared by precipitation method to improve the absorption ability of VO3/Bi2WO6 to visible light to a great extent. Photocatalytic experiments showed that the appropriate amount of Ag3PO4 modified WO3/Bi2WO6 had the best effect on the degradation of RhB, which was due to the uniform dispersion of appropriate amount of Ag3PO4 nanoparticles on flower-like WO3/Bi2WO6 microspheres and nanoparticles. In addition, the conduction band in Ag3PO4-WO3-Bi2WO6 ternary composite photocatalyst can form a hierarchical structure, and electrons can transfer from Bi2WO6 band to Ag3PO4, band and then to WO3 band, thus effectively promote the separation of photogenerated carriers. In conclusion, a series of novel floral WO3/Bi2WO6-based ternary heterojunction photocatalysts have been studied in this paper, which can effectively improve the absorption of visible light and the quantum efficiency of WO3/Bi2WO6.
【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36;O644.1

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