Preparation And Photocatalytic Activity Of Iodine-Controlled Oxygen-deficient Bismuth Molybdate And Bismuth Tungstate Materials

Photocatalysts have shown great potential in solving environmental and energy problems in recent years.TiO₂,a common wide band gap semiconductor with a narrow spectral response is limited in its application.As a a new type of visible light photocatalyst,bismuth-containing materials,have been widely used in heterogeneous photocatalytic reactions such as reduction of CO₂,degradation of pollutant and removal of NO because it is safe,non-toxic,structurally stable and easy to control energy band.The morphology,crystal plane and electronic structure are very easy to control especially for the Aurivillius layered structural materials such as bismuth tungstate and bismuth molybdate.Researchers have done a lot of modification research of these materials like constructing composite system,regulating morphology structure,mixing foreign element and building surface defect.Among them,halogen doping and surface oxygen vacancy construction are common ways to improve the photocatalytic performance of materials.Starting from defect construction induced by iodine,this paper designed and synthesized the oxygen vacancy bismuth tungstate and bismuth molybdate materials.Through a series of characterization experiments,iodine can promote a large amount of oxygen vacancies in the material and improve the photo-electron separation efficiency of the material,which can further improve its photocatalytic performance.The specific research content of this paper is as follows:1)Firstly,iodine can promote the formation of oxygen vacancies with theoretical simulation study on the effect of iodine introduction on the formation of oxygen vacancy in?-phase bismuth molybdate??-Bi₂MoO₆?.Under the guidance of the calculation results,potassium iodide was used as the iodine source to control the synthesis of bismuth molybdate materials with different oxygen vacancy concentrations.The effects of iodine on the crystal structure,morphology and surface element composition of bismuth molybdate were studied through characterization such as XRD,SEM,TEM,XPS and ESR.It was found that the introduction of iodine did not affect the crystallization and composition of the material,but significantly promoted the formation of oxygen vacancies on the surface of the material.With the photocatalytic degradation of acetaminophen,the degradation rate of oxygen vacancy bismuth molybdate under visible light conditions was7.3 times higher than that of pure bismuth molybdate,and photogenerated holes were the main active species.At the same time,the photocatalytic degradation mechanism of iodine-induced oxygen vacancy bismuth molybdate was deduced by characterization experiments including Electron Spin Resonance?ESR?,photocurrent detection,photoluminescence spectrum?PL?,active species capture,and electrochemical impedance spectroscopy?EIS?.2)Bismuth tungstate?Bi₂WO₆?is easier to do iodine doping than?phase bismuth molybdate by the theoretical simulation calculation of the formation energy of iodine doping.According to the results,we synthesized bismuth tungstate materials doped with different concentrations of iodine by solvothermal method.With characterization,iodine is doped into the bismuth tungstate crystal,and the introduction of iodine can enhance the absorption of the visible light region of the material.Through the degradation of sodium pentachlorophenolate,it was found that the total organic carbon removal rate of iodine-doped bismuth tungstate under visible light conditions was 10.6 times faster than that of pure bismuth tungstate,and the photocatalytic performance of the material increased first and then decreased with the increase of iodine doping concentration.At the same time,a series of characterization experiments were carried out to study the synergistic effect of iodine doping and oxygen vacancies and to presume the mechanism of photocatalytic degradation of sodium pentachlorophenol by iodine-doped oxygen vacancy bismuth tungstate.