Research On The Preparation And Photocatalytic Performance Of BiOI

Photocatalysis has become the first choice for solving energy and environmental problems due to its green,high efficiency and low price.Exploring new photocatalysts or modifying existing photocatalysts has become a current research topic.As a kind of bismuth oxyhalide photocatalyst,Bi OI not only has its own properties such as high efficiency,non-toxicity and low cost,but also has high visible light response characteristics that similar materials Bi OCl and Bi OBr do not have.At the same time,Bi OI has its own properties in photocatalysis due to its unique layered structure and special energy band structure.However,Bi OI itself has its own shortcomings,such as high photo-generated carrier recombination rate and poor redox ability,which limits its photocatalytic activity.Therefore,it is necessary to modify it.Based on this research background,the main research content of this paper is the preparation,morphology and Br doping modification of Bi OI,and exploring the mechanism of its photocatalytic activity improvement.The specific research content of this article are as follows:(1)Mainly using hydrothermal method by changing the order of addition of solvents(water and ethylene glycol),successfully prepared Bi OI with two morphologies of nanosheets and nanoflowers,and through XRD,SEM,Raman,XPS and other means analyze its phase composition,morphology,element valence,etc.The morphology and composition evolution process were observed by changing the reaction temperature and reaction time,the possible mechanisms of the two morphologies of Bi OI nanosheets and nanoflowers were analyzed.The results show that the formation of nanosheets and nanoflowers is due to the difference in the diffusion rate of I ions in ethylene glycol and water,resulting in different sizes and thicknesses of nanosheets.Large and thin nanosheets self-assemble into nanoflowers,and small and thick nanosheets continue to grow.(2)The hydrothermal method was mainly used to prepare samples of Br-doped Bi OI with different content of Br,a series of characterization analyses were carried out on them by means of XRD,SEM,Raman,XPS,UV-Vis DRS etc.such as phase composition,crystal structure,morphology,element chemical valence,optical properties,internal molecular vibration,etc.Rhodamine B was used as the degrading substance,and the prepared samples were subjected to photocatalytic degradation to determine the level of photocatalytic activity.The active species trapping experiment is used to determine the type of active groups that play a role.The mechanism of Br-doped Bi OI improving its photocatalytic performance is clarified from the perspective of energy band structure.Experimental results show that proper Br doping willgenerate more oxidative photogenerated holes and hydroxyl radicals by downing the valence band,And Br doping makes the band gap of Bi OI moderately widened,and prolongs the recombination path of photogenerated electrons and holes,so reduce the recombination rate of both.