Preparation And Properties Of Metal-free Composite Photocatalyst Based On Boron Nitride And Their Degradation Performance Of Typical PPCPs

The widespread presence of drugs and personal care products（PPCPs）in environmental waters has attracted worldwide attention.With the progress and development of science,PPCPs are gradually attracting people’s attention because of the pseudo-persistent phenomena and physiological toxicity caused by them.Therefore,in order to solve these problems,it is necessary and significant to develop effective strategies and solutions.Photocatalysis is considered as an ideal green and sustainable way to solve the global environmental pollution and energy shortage and has attracted wide attention.The preparation of photocatalyst is the most important part of photocatalysis technology.Hexagonal boron nitride（BN）,the so-called"white graphene",is a representative 2D crystal,has great potential due to its adjustable band gap,excellent chemical stability and thermal stability.Metal doping is easy to cause pollution and poisoning to the water body.For the purpose of avoiding secondary pollution to the water environment,non-metallic BN is modified with non-metallic elements and uses its own characteristics to synthesize non-metallic photocatalysts to expand Used in the construction of photocatalysts,designed highly active photocatalytic materials and applied them to the degradation of typical PPCPs.The main research contents and results are as follows:（1）Using a simple hydrothermal calcination synthesis strategy,using semiconductor graphite carbon nitride（CN）which is rich in carbon elements,the carbon element is synthesized in the form of a CNB bond to modify BN to regulate its band gap,and at the same time a small amount of CN is generated Due to the formation of subtle heterojunctions.Carbon nitride composite boron nitride photocatalyst（CMBN）has a wider absorption wavelength range than BN.Under blue LED visible light,CMBN composite material has a higher degradation activity for ENFX.The photocatalytic performance of the optimal ratio of 3-CMBN composite material is 39.3 times and 2.4 times that of the original BN and CN,respectively.The most basic reason for the enhancement of catalytic activity is that carbon element regulates the band gap of BN.The identification results of active species show that h⁺and O₂^·-play a leading role in the process of catalytic degradation.In addition,by identifying ENFX’s degradation intermediates and using density functional theory to predict the reaction site,the degradation path was inferred,including hydroxyl addition and ring cleavage.Repeated testing of surface composite materials has good stability and can be applied to environmental restoration.（2）The low utilization rate of photogenerated carriers is still the main challenge of low photocatalytic activity.In order to maximize the use of photocatalysts,carbon dots（CDs）and boron nitride（BN）were selected as photo-generated electron and photo-generated hole transport carriers,respectively,and then combined with graphitized carbon nitride（g-C₃N₄）mixed to form non-metallic and high efficiency ternary photocatalytic material"CDs/g-C₃N₄/BN"with photo-generated carrier double transfer mechanism.The rate constant of this non-metallic composite catalyst to enrofloxacin under blue LED irradiation is about 5 times higher than the original g-C₃N₄.The enhancement of photocatalytic activity is mainly due to the coordinated transfer of photogenerated carriers by CDs and BN to improve the separation efficiency of electron-hole pairs and enhance the ability of generating active oxygen species.Moreover,the composite photocatalyst shows good stability.Through the identification of intermediate products in the degradation process and the speculated reaction path of the reaction site,including hydroxylation and C-N bond cleavage.