Preparation And Photocatalytic Properties Of Carbon Quantum Dots Composite BiOIO₃ Materials

With the depletion of global fossil energy,the development of new energy has become a top priority,among which solar energy,wind energy and other clean energy are the targets of vigorous development.Photocatalysis is a technical means to degrade pollutants through oxidation and reduction reaction using sunlight.It has been widely studied and applied due to its advantages of environmental protection and low cost.Among them,BiOIO₃ photocatalyst material has become a hot material recently due to its high VB value,unique chemical structure and strong stability.But at the same time,its wide band gap structure also limits its application in visible light,so it is very important to design appropriate modification methods for the application of bismuth oxyiodide.In this project,BiOIO₃ materials were motified by simple loading,construction of S-scheme heterojunction and construction of magnetic three-channel photocatalysis materials.Thus,a series of different photocatalysis composites using carbon quantum dots,g-C₃N₄ and Fe₃O₄(N-CQDs/BiOIO₃,BiOIO_3-x/N-CQDs/g-C₃N₄ and BiOIO_3-x/N-CQDs/Fe₃O₄)were synthesized respectively.Tetracycline aqueous solution（TC）was taking as the target pollutant,it is finally proved that the prepared photocatalyst has more excellent photodegradation effect,and its possible photocatalytic mechanism was proposed,which lays the foundation for further high efficiency in pollutant degradation,environmental protection and other ecological aspects.The specific research contents are as follows:（1）The 0D/2D N-CQDs/BiOIO₃ composite was synthesized by a simple surfactant assisted hydrothermal method.Through characterization and analysis by means of XRD,FT-IR,BET and TOC,it was found that when the amount of 0.51 mg/L carbon quantum dot aqueous solution was 10 m L,the photocatalytic efficiency of N-CQDs/BiOIO₃ composite was the highest,and it could degrade 70%of TC aqueous solution within 120 min,which was 20%higher than that of pure BiOIO₃.Moreover,the method has the advantages of easy availability of raw materials,low cost and simple preparation process.Finally,the possible degradation mechanism of the composite material to TC solution was proposed based on the results of the active material capture experiment.（2）BiOIO₃ with oxygen vacancies was prepared by high-temperature calcination,then N-CQDs were anchored on the surface of BiOIO_3-x,and finally S-scheme heterostructures were constructed with g-C₃N₄ matching the band gap structure.In this way,the photocatalytic efficiency of the prepared products could be greatly improved in a short time.The photocatalytic results showed that the ternary composite BiOIO_3-x/N-CQDs/g-C₃N₄ reached the best degradation efficiency when the reaction conditions were 150℃and 8 h,and it could degrade 70%tetracycline aqueous solution in 60 min.Finally,XRD,FTIR,XPS,TEM and other characterization experiments proved that the S-scheme heterojunction ternary composite BiOIO_3-x/N-CQDs/g-C₃N₄ was successfully synthesized.（3）The BiOIO_3-x/N-CQD/Fe₃O₄ ternary composite with three channel structure was constructed by three electron transfer modes,namely,BiOIO_3-x with rich oxygen vacancies,the electronic medium of N-CQDs and the redox center of Fe₃O₄.The recyclability of the photocatalyst material can also be improved by the magnetism of Fe₃O₄.When the reaction temperature is 150℃and the reaction time is 8 h,the degradation efficiency of tetracycline aqueous solution is the highest,which can reach 74%in 60 min.In addition,the degradation rate remains at 58.63%after five recovery experiments,which proved that the ternary BiOIO_3-x/N-CQDs/Fe₃O₄ composite photocatalytic material has excellent photocatalytic performance and good stability.