Preparation Of BiOBr-based Photocatalyst And Degradation Of Organic Pollutants In Water

The gradual deterioration of global environmental pollution and energy shortages arouses human crisis awareness.For the sustainable development of human society,an imperious demand has been required to develop pollution-free environmental remediation technologies and alternative clean energy supplies.Among the various green earth and renewable energy projects underway,semiconductor photocatalysis has become one of the most promising technologies.It represents a convenient way to solve environmental and energy problems by using natural sunlight or artificial lighting energy,and can be widely used all over the world.Most traditional photocatalysts,such as Ti O₂ and Zn O,can only absorb ultraviolet light,greatly limiting the application of photocatalytic technology.Due to the absorptivity to visible light,BiOBr has attracted a lot of attention.However,pure BiOBr can only absorb limited visible light,and the recombination of photo-generated electron-hole reduces the electron-hole lifetime and photocatalytic activity,which is a crucial factor that limits the photocatalytic efficiency of BiOBr’s in the degradation of pollutants.Semiconductor coupling,as a representative of photocatalytic modification,is one of the main methods to promote photo-generated electron-hole separation and inhibit the recombination.We prepared BiOBr-based composite nanomaterials by constructing a heterojunction through semiconductor coupling to improve the efficiency of photogenerated electron-hole separation and catalytic activity.The main conclusions are as follows:1.The high-efficiency binary Bi₂Fe₄O₉/BiOBr Z-scheme heterojunction was prepared by a simple hydrothermal method.The obtained Bi₂Fe₄O₉/BiOBr exhibited high catalytic activity in the photodegradation of rhodamine B（Rh-B）and tetracycline hydrochloride（TC）.90%of Rh-B was photodegraded by Bi₂Fe₄O₉（40mg）/BiOBr within40 minutes,which was more efficient than pure Bi₂Fe₄O₉ and BiOBr.The effective light-induced electron-hole separation,widened light absorption range,high hole oxidation ability and high electron reduction ability were ascribed to the formation of the Z-scheme system and improved catalytic activity.Radical trapping and electron spin resonance spin trapping experiments showed that holes（h⁺）,hydroxyl radicals（·OH）and superoxide radicals（·O₂^-）were the main active free radicals in the catalytic system.2.The Z-scheme heterojunction SnFe₂O₄/BiOBr,which was non-toxic,magnetic,and photocatalysis under visible light,was synthesized and optimized by a two-step solvothermal method.SnFe₂O₄（20 mg）/BiOBr heterojunction showed the best visible light photocatalytic performance in degradation of Rh-B with a removal efficiency of91%.In addition,an external magnetic field can easily recover SnFe₂O₄（20 mg）/BiOBr heterojunction from the solution due to the magnetic property.After recycling,the photocatalytic activity almost kept unchanged.This work showed that the close contact heterojunction based on ferrite can be a promising photocatalyst in environmental and energy applications.3.A direct double Z-scheme photocatalyst BiOBr/g-C₃N₄/Bi₂WO₆ was prepared by a simple one-pot hydrothermal precipitation method.Compared with pure Bi₂WO₆,BiOBr,g-C₃N₄,g-C₃N₄/Bi₂WO₆ and BiOBr/g-C₃N₄/Bi₂WO₆ composites,BiOBr/g-C₃N₄/Bi₂WO₆ exhibited higher photocatalytic activity under visible light irradiation in TC degradation.When adding 20 mg of BiOBr/g-C₃N₄/Bi₂WO₆catalyst,the degradation rate of TC（20 mg/L）within 40 min achieved 91%.The enhanced photocatalytic performance of BiOBr/g-C₃N₄/Bi₂WO₆ ternary composites was ascribed to the ternary composite structure,which can generate more electrons and holes in virtue of the enhanced visible light absorption,and.the continuous direct double-Z heterojunction structure,which can effectively separate the photogenerated electron-hole pairs and improve the redox ability.