Preparation Of Iodine Iodine Oxide And Its Growth Mechanism And Photocatalytic Properties

Environmental problems and energy crisis are two major problems that contemporary society faces and urgently needs to solve.Due to the use of solar energy,strong oxidation ability and no secondary pollution,the semiconductor photocatalytic technology has been developing rapidly.However,its wide application is limited owing to low utilization rate of traditional photocatalyst.Therefore,it is a key to investigate photocatalysts with visible light response.The photocatalytic activity of semiconductor materials is closely related to its structure,so the preparation of new photocatalytic materials with special structure,high specific surface area has become the new way to obtain efficient photocatalyst.In recent years,with the development of nano-photocatalysis,three-dimensional(3D)micro/nano-structure as a special group due to small size and specific surface area has attractedmore interest of many scientific researchers.Bismuth iodide as a semiconductor photocatalysishas become promising photocatalysts for a highly anisotropic layered structure and a narrow band gap,which can effectively utilize the sunlight.In this dissertation,BiOI photocatalysts were prepared by hydrothermal method(solvothermal method)with changing the reaction conditions or adding auxiliary agent for urea and formic acid.The samples were characterized by XRD,SEM,TEM,UV-vis DRS and BET to study the influence of reaction conditions and auxiliary materials on the phase structure,morphology,band gap and BET.The photocatalytic ability of samples was analyzed by degradation of MO and RhB,thus providing a theoretical basis and experimental conditions for the development and preparation of novel visible light photocatalyst.The main contents include the following three parts:(1)BiOI samples with different morphologies have been prepared by hydrothermal method.The influence of pH values on phase structure,microstructure,specific surface area and optical properties is systematically studied.The results show that when the pH is 1?10,the samples are tetragonal phase,the size of BiOI sheet becomes smaller and thinner with the increase of pH value and then BiOI sheets aggregates into microspheres.When pH = 10,the netstructure of microspheres begins to disappear and BiOI sheets begin to be thicken.When the pH = 13,the sample is orthorhombic phase of Bi5O7I.The growth mechanism is mainly the role of pH and self-assembly.The photocatalytic performance of the products with methyl orange(MO)as the target shows that when pH=7,the photocatalytic performance is the best,relating to its high specific surface area and grain size.(2)BiOI microspheres with double structure were firstly prepared with urea by solvothermal method.The effect of urea on the phase structure,microstructure,specific surface area and optical properties is systematically studied.The results show that the samples are tetragonal phase BiOI,the sample is irregular flower structure,easy to reunite without urea,the sample are two different sizes of microsphere with urea,which are regular,uniform size and gooddispersibility.The growth mechanism of three-dimensional spherical structure is analyzed by time series experiment,which indicates that urea has an important effect on the nucleation,growth and self-assembly process during the reaction.The photocatalytic activity of samplesare investigated under visible light irradiation by degradation of methyl orange(MO)and rhodamine B(RhB).The results show that the photocatalytic activity of the urea-added sample decreases with wide band gap and grain size.(3)BiOI microspheres with three-dimensional structure were prepared with formic acidby solvothermal method.The effect of formic acid on the phase structure,microstructure and specific surface area is studied systematically.The results show that the prepared samples are tetragonal phase.The sample without formic acid is irregular flower structure,easy to agglomerate.The sample with formic acid is regular microspheres,uniform size and good dispersibility.The formation mechanism of three-dimensional spherical structure is studied by time series experiment,which shows that formic acid plays a key role on the nucleation,growth and self-assembly process during the reaction.The photocatalytic activity is investigated by degradation of methyl orange(MO)and rhodamine B(RhB)under visible light irradiation.The results show that the photocatalytic activity of theHCOOH-added sample decreases with its smaller specific surface area and grain size.