Modification And Photocatalytic Performance Of Bismuth Oxycarbonate Based Composite Catalyst

As a green technology,photocatalysis technology is based on the strong redox ability of semiconductor photocatalysts obtained under light conditions.Photocatalysts can react with water and oxygen adsorbed on the surface to generate active substances to degrade pollutants into carbon dioxide and water,thereby achieving the goals of purifying pollutants,material synthesis,and conversion.As a bismuth-based material,bismuth oxycarbonate(Bi2O2CO3,or BOC for short)with its low price and special structure attracts the attention of researchers.However,single-system BOC has a high band gap width that requires high energy for the excitation of photogenerated carriers,which is the main reason for restricting the development of photocatalysts.Therefore,compounding and modifying bismuth oxycarbonate to adjust the morphology and form multiple heterojunctions can promote the migration of photogenerated carriers,which is expected to improve the photocatalytic performance and then make it more widely used.The main research results are shown as follows.Ⅰ.Preparation and mechanism of BiOCl/BOC heterogeneous photocatalystDue to the different electronegativities of cations,the exchange between Cland CO32-is controlled,thereby achieving the goal of regulating the ratio of BiOCl to BOC.Meanwhile,different kinds of cations affect the growth orientation of the lamellae during the halogenation process,which results in different morphologies.Among them,BiOCl/BOC using LiCl as a chlorine source obtains stable flowerlike morphology.Moreover,the introduction of oxygen vacancies during the selfassembly process of the sheet layer changes the surface environment of the photocatalyst and improves its photocatalytic performance.After 100 minutes of visible light irradiation,CBOCL-4 can completely degrade Rh B.Ⅱ.Modification and mechanism of BiOCl/BOC heterogeneous photocatalystSurfactants are used as modifiers to mediate the reaction rate of BOC halogenation,which regulates the size and stacking of the sheets.Indeed,surfactants bring in oxygen vacancies during the reassembly process of the sheets,which effectively adjusts the surface properties of the composite.Meanwhile,the generated oxygen defect energy level promotes the migration of photogenerated carriers and reduces recombination.Furthermore,surface modification results in a more open flower-like structure center and a loose stacking of the sheets,which further promotes the exposure of active sites in the material.Therefore,SBOCC2 completely degrades Rh B after 80 min of illumination,further shortening the degradation time.Ⅲ.Preparation and mechanism of Bi/BiOCl/BOC heterogeneous photocatalystBOC is partially reduced in situ through a bi-bismuth source and a reducing solvent to maintain the stability of the three-dimensional flower-like structure of the Bi/BiOCl/BOC.Due to the introduction of bismuth,the surface properties of BOC are activated,which promotes the subsequent conversion of Bi/BOC to BiOCl,thereby promoting the formation of heterojunctions.Furthermore,the SPR effect of bismuth regulates the heterojunction energy band structure and even promotes the migration of photogenerated carriers.Among them,BBOCE-2 can completely degrade RhB under visible light for 60 minutes and also exhibit excellent photocatalytic performance for tetracycline hydrochloride and norfloxacin in antibiotics.In summary,based on the research of flower-like bismuth oxycarbonate,composite materials with excellent photocatalytic properties are obtained by adjusting the morphology and heterojunction structure.Moreover,the mechanism of photocatalytic composites is simulated and explored based on factors such as micromorphology,phase composition and photoelectric properties.This work prepares bismuth oxycarbonate-based composite materials in a neutral environment,demonstrating efficient photocatalytic degradation of various pollutants,which provides new ideas for the design and industrial application of photocatalysts.