Preparation And Properties Of Periodic Bismuth-Based Composite Photocatalysts

With the continuous development of the economy,global environmental pollution and energy crises have become increasingly serious,which has become an important issue restricting human survival and development.Visible light-driven semiconductor photocatalysis technology has the characteristics of low energy consumption,high efficiency,and no secondary pollution,which has been recognized as one of the most effective means to solve current environmental and energy problems.So far,researchers have developed photocatalytic materials of different systems.Iodine bismuth oxide(Bi₅O₇I)standed out among many photocatalytic materials due to its unique internal layered structure and potential photocatalytic activity.However,the wide band gap of Bi₅O₇I limited its absorption in the visible light region.Thus,In this study,Bi₅O₇I/Ag and Bi₅O₇I/Ag/CdS composite photocatalysts were constructed by loading Ag nanoparticles and CdS quantum dots on the surface of Bi₅O₇I nanosheets.The introduction of the Ag nanoparticles and CdS quantum dots expanded the visible light response range of the composites,and also improved the separation efficiency of the electron-hole pair of Bi₅O₇I.Finally,the possible photocatalytic mechanism was explored through the degradation analysis of pollutants.This paper mainly discusses from the following aspects:(1)Using bismuth nitrate pentahydrate and potassium iodide as source for the synthesis of Bi₅O₇I,Bi OI was first prepared by the oil bath method,and then the Bi OI was calcined at 450?for 3 h to obtain Bi₅O₇I microspheres.The Bi₅O₇I/Ag binary composite photocatalyst was prepared by depositing Ag nanoparticles on the surface of Bi₅O₇I microspheres by photoreduction method.The Bi₅O₇I/Ag composite photocatalyst exhibited good visible light photocatalytic activity,and the degradation efficiency of bisphenol A and 2,6-dichlorophenol reached 54.7%and 50.5%,respectively,the photocatalytic hydrogen evolution rate of Bi₅O₇I/Ag(3)is as high as 165.2?mol h^-1g^-1,which was significantly better than the pure Bi₅O₇I.The reason for the enhanced performance of the composite photocatalyst can be attributed to the three-dimensional bulbous structure of Bi₅O₇I and the surface plasmon resonance(SPR)effect of Ag nanoparticles,which extend the visible light response range of composite materials and improved its electron-hole pairs separation.(2)Using the synthesized Bi₅O₇I/Ag as the precursor,CdS quantum dots were introduced on the surface of Bi₅O₇I/Ag by hydrothermal method to form a Bi₅O₇I/Ag/CdS ternary composite photocatalyst.Bi₅O₇I/Ag/CdS exhibited excellent visible light photocatalytic activity,and the degradation efficiency of bisphenol A and 2,6-dichlorophenol reach 98.2%and 96.5%,respectively.In addition,the photocatalytic hydrogen evolution rate of Bi₅O₇I/Ag/CdS is also as high as 456.4?mol h^-1g^-1.A possible mechanism of enhanced photocatalysis was proposed based on related performance tests and energy band theory.The formation of a series heterojunction between Bi₅O₇I and CdS promotes the separation of photogenerated charge carriers.In addition,the unique structure of Bi₅O₇I and the SPR effect of Ag nanoparticles also played an important role.