【作者】 李阳；

【导师】 肖新颜；

【作者基本信息】 华南理工大学 ， 化学工程， 2018， 硕士

【摘要】 近年来,工业文明的高速发展导致的环境污染和能源短缺等问题日益突出。半导体光催化技术作为一种能持续利用可再生太阳能进行污染治理和环境保护的绿色技术,能为人们解决以上问题提供可行性方案。然而,以TiO₂为主的半导体带隙较宽（³.2 eV）,仅能利用只占太阳辐射总量约5%的紫外光,导致太阳能利用率不高。钒酸铋（BiVO₄）作为一种新型的可见光半导体材料,能够吸收可见光,开发研究具有高效可见光活性的BiVO₄基复合光催化材料,对于提高太阳能利用率具有重要意义。为此,本文开展了BiVO₄复合改性及其光催化机理的研究工作。主要研究内容如下:采用多元醇法制备了四方白钨矿型钒酸铋（（t-s）BiVO₄）,热缩聚法制备了类石墨相氮化碳（g-C₃N₄）,简单的超声辅助化学吸附法制备了具有核壳结构的（t-s）BiVO₄/g-C₃N₄复合光催化剂。采用XRD、SEM、FT-IR、XPS、PL以及电化学测试对光催化剂样品的结构和性能进行了表征;以罗丹明B（RhB）为目标污染物,对复合光催化剂的光催化活性进行了评价;通过自由基捕获实验,对复合光催化材料的光催化机理进行了研究。实验结果表明,通过二者的复合,复合光催化材料的光催化性能得到显著提高。当（t-s）BiVO₄与g-C₃N₄的质量比为1:16时,（t-s）BiVO₄/g-C₃N₄复合光催化剂具有最高的光催化活性,在模拟太阳光照下,120 min内对RhB的降解效率为97.7%。此外,自由基捕获实验结果表明,h⁺和·O₂^-是光催化反应过程中的主要活性物种。（t-s）BiVO₄/g-C₃N₄复合光催化剂具有较强的光催化活性以及光催化稳定性,这可能归因于在二者复合的接触界面形成了异质结构,拓展了复合光催化材料光吸收范围,并且在一定程度上促进了光生载流子分离,抑制了光生载流子复合的缘故。采用改进Hummers法制备了氧化石墨烯（GO）,采用高温煅烧法制备了单斜白钨矿型钒酸铋（（m-s）BiVO₄）,采用3-氨基丙基三乙氧基硅烷（KH550）修饰辅助的溶剂热法制备了BiVO₄/RGO复合光催化剂,进一步通过原位离子顺序沉淀法制备了BiVO₄/RGO/Ag₃PO₄复合光催化剂。采用SEM、XRD、FT-IR、XPS、UV-vis以及PL对光催化剂样品的结构和性能进行了表征;以RhB和4-硝基酚（4-NP）为目标污染物,对单纯Ag₃PO₄和BiVO₄,BiVO₄/RGO、BiVO₄/Ag₃PO₄以及BiVO₄/RGO/Ag₃PO₄复合光催化剂的光催化活性进行了评价;通过自由基捕获实验,对复合光催化材料的光催化机理进行了研究。实验结果表明,不同质量配比的BiVO₄/RGO/Ag₃PO₄复合光催化剂的光催化活性都高于相应的BiVO₄/Ag₃PO₄复合光催化剂以及单纯的Bi VO₄和Ag₃PO₄,并且当Ag₃PO₄与BiVO₄/RGO质量比为0.6∶1时,BiVO₄/RGO/Ag₃PO₄复合光催化剂的光催化活性最高,45 min内对RhB的降解效率为98.2%,对4-NP的降解效率为82.1%。自由基捕获实验结果表明,h⁺和·O₂^-是光催化反应过程中的主要活性物种。三元复合光催化剂光催化性能以及光化学稳定性的增强可能归因于BiVO₄与Ag₃PO₄二者之间的协同效应,以及RGO的引入能够促进光生电子的快速转移,抑制光生电子-空穴对的复合的缘故。更多还原

【Abstract】 In recent years,problems such as environmental pollution and energy shortage caused by the rapid development of industrial civilization have become increasingly prominent.As a green technology that can sustainably utilize the renewable solar energy for pollution control and environment protection,semiconductor photocatalytic technology can provide a feasible solution to solve the above problems.However,the wide bandgap of TiO₂（≈3.2 eV）makes it possible to use only the UV radiation which is just about 5%of the total solar radiation,and results in a low utilization efficiency of solar energy.BiVO₄ is a new type of visible light responsive semiconductor material,which can absorb the visible light.The development of BiVO₄ based composite photocatalysts with high visible light photocatalytic activity are of great significance for improving the utilization efficiency of solar energy.Therefore,the coupling modification and its photocatalytic mechanism of BiVO₄ semiconductor materials were studied in this article.The main research contents are as follows:The tetragonal scheelite bismuth vanadate（（t-s）BiVO₄）and graphite-like phase carbon nitride（g-C₃N₄）were prepared by a polyol method and thermal condensation method,respectively,and then the（t-s）BiVO₄/g-C₃N₄ composite photocatalysts with core-shell structure were successfully synthesized via a facile combination of ultrasonic and chemisorption treatment.The structure and properties of the as-obtained photocatalyst samples were characterized by XRD,SEM,FT-IR,XPS,PL and electrochemical tests.The photocatalytic activities of composite photocatalysts were investigated using Rhodamine B（RhB）as the target contaminant,and its photocatalytic mechanism was studied by the radical capture experiments.The experimental results showed that the photocatalytic performance of the composite photocatalysts had been significantly improved.When the mass ratio of（t-s）BiVO₄ to g-C₃N₄ was 1:16,the photocatalytic activity of the composite photocatalysts was highest.Under the simulated sunlight irradiation,the degradation efficiency for RhB was97.7%within 120 min.In addition,capture experiments showed that h⁺and·O₂^-were the main active species in the photocatalytic reaction process.（t-s）BiVO₄/g-C₃N₄ composite photocatalyst had an enhanced photocatalytic activity and stability.This can be attributed to the formation of the heterojunction structure at their interface,which can extend the light absorption range of the composite photocatalysts,promote the separation and suppress the recombination of photogenerated carriers to some extent.Graphene oxide（GO）was prepared by a modified Hummers method.The monoclinic scheelite type bismuth vanadate（（m-s）BiVO₄）was prepared by a calcining method,and then BiVO₄/RGO composite photocatalysts were prepared by 3-aminopropyltriethoxysilane（KH550）modification assisted solvothermal method.BiVO₄/RGO/Ag₃PO₄ composite photocatalysts were synthesized by in-situ ion sequential precipitation method.The structure and properties of the photocatalyst samples were characterized by XRD,SEM,FT-IR,XPS,UV-vis and PL.The photocatalytic activities of BiVO₄/RGO/Ag₃PO₄ composite photocatalysts were investigated using RhB and 4-nitrophenol（4-NP）as the target contaminants,and the photocatalytic mechanism was studied by the radical capture experiments.The experimental results showd that the photocatalytic activities of BiVO₄/RGO/Ag₃PO₄ composite photocatalysts with different mass ratios were higher than that of BiVO₄/Ag₃PO₄ composite photocatalysts,pure BiVO₄ and Ag₃PO₄,and the photocatalytic activity of the composite photocatalysts was highest,and the degradation efficiency for RhB was 98.2%in 45 min when the mass ratio of Ag₃PO₄ and BiVO₄/RGO was0.6:1.During the process of photocatalytic reaction,h⁺and·O₂^-were the dominant active species.The enhanced photocatalytic performance of BiVO₄/RGO/Ag₃PO₄ composite photocatalysts can be assigned to the synergy effect of BiVO₄ and Ag₃PO₄,incorporation of RGO which can promote the transfer ability of photogenerated electrons,inhibiting the recombination of photogenerated electron-hole pairs.更多还原