Fabrication Of BN Quantum Dots Decorated 2D Nanosheets And Their Photocatalytic Performance Improvement

Under the excitation of inexhaustible solar energy,semiconductor photocatalysis technology has gradually been regarded as an important method to alleviate the environmental and energy crisis with considerable catalytic efficiency,green and sustainable characteristics.However,in practical applications,the biggest bottleneck of semiconductor photocatalytic technology is how to suppress the recombination of photogenerated electron-hole pairs on the basis of making full use of solar energy.Generally,the morphology and structure of semiconductor nanomaterials are one of the important factors,because the effective improvement of morphology and structure could promote the rapid transfer and separation of photogenerated charges.Typically,the development of 0D and 2D structural materials is representative:on the one hand,0D materials,especially 0D quantum dot materials,exhibit excellent photochemical stability because of quantum confinement,large specific surface area,and surface effects;On the one hand,2D nanomaterials are extremely beneficial in enlarging the photoresponse region,shortening the transport distance of photogenerated carriers from the bulk phase to the surface,and exposing more active sites,which make them a stable substrate material.This dissertation focused on improving wastewater pollution in the environment.In order to solve the problems of low solar energy utilization,high carrier recombination,and insufficient active sites that restricted the photocatalytic redox ability,this research took the photogenerated hole transfer characteristics of zero-dimensional BNQDs as the main starting point,and assisted Bi₂Mo O₆,Bi₂WO₆,and g-C₃N₄2D nanosheet materials to build different carriers separation mechanisms,so as to effectively improve the photoelectric performance and redox ability of the catalyst.Finally,the typical antibiotics and heavy metal Cr（VI）pollutants in the environment could be removed efficiently.The main research contents of the thesis were as follows:（1）The hydrothermally synthesized 0D BNQDs were successfully combined with 2D Bi₂Mo O₆nanosheets by electrostatic adsorption.Besides,the analysis of phase composition,morphology and structure,chemical composition,and photoelectric properties indicated that 0D BNQDs were well dispersed on 2D Bi₂Mo O₆nanosheets with large-area,and there was a stable chemical interaction with each other.Furthermore,the catalytic efficiency of the composite photocatalytic nanomaterials for degrading antibiotics was explored under visible light irradiation.As a result,it could be found that the photogenerated carriers were efficiently separated,facilitating the TC degradation efficiency to reach 3.1 times that of pure Bi₂Mo O₆within 25 minutes.In brief,the photocatalytic activity was remarkably boosted because of the hole attraction by BNQDs and the advantages of the 0D/2D structure for carrier extraction and transfer.（2）Based on the mechanism of Bi₂Mo O₆/BNQDs,the removal of antibiotics mainly relied on photocatalytic active substances with strong oxidizing properties.Therefore,Bi₂WO₆with more positive oxidation potential was carried out to further explore the separation of carriers and photocatalytic mechanism.And the results suggested that the photocatalytic degradation of antibiotics mainly depended on the separation efficiency of photogenerated electron-hole pairs.What’s more,the BNQDs/Bi₂WO₆composites displayed excellent separation of photogenerated electron-hole pairs and active sites exposure with the help of BNQDs.Finally,the oxidative degradation efficiency of BNQDs/Bi₂WO₆was significantly higher than that of Bi₂WO₆.（3）It was noted that the main challenge of photocatalytic was to maximize the extraction of charge carriers and enable them to efficiently participate in redox reactions.Accordingly,this work broke the limitation of the single charge transfer mode and developed a dual carrier transfer channel to enhance photocatalytic activity.In detail,BNQDs and Ag were introduced into ultra-thin g-C₃N₄nanosheets as dual co-catalysts to facilitate carrier transport.Typically,the electron potential well generated by Ag was beneficial to pull the charge to transfer rapidly on a large area of the g-C₃N₄surface.Meanwhile,the BNQDs with photoinduced hole extraction property could help to separate the photogenerated holes.As a result,a dual-channel separation method for electron and hole transfer was constructed,which promoted g-C₃N₄/Ag/BNQDs to exhibit stronger oxidative and reductive abilities.Under the promotion of dual channels,the antibiotic oxidative degradation and Cr（Ⅵ）reduction removal rate reached 80.54%and 88.93%within 60 minutes,respectively.Briefly,the introduction of dual co-catalysts synergistically improved the dissociation efficiency of photogenerated electron-hole pairs,ensuring that more photogenerated charges and holes effectively participated in the photocatalytic reaction.