The Enhanced Photocatalytic Activity Of Bi₂O₃ Decorated By MXene Quantum Dots And Its Degradation And Mechanism Of Tetracycline

At present,organic pollutants such as antibiotics dissolved in water have become a difficult problem in water pollution treatment.Solar-light-driven photocatalytic technology has the advantages of sustainability,high efficiency and greenness,making it an ideal method to deal with antibiotic pollution.Owing to the suitable band gap,chemical stability,and response to visible light,Bi₂O₃ has enormous application potential in water treatment.However,the weak visible adsorption and rapid photogenerated carrier recombination weaken its photocatalytic activity.Adding co-catalyst to promote the separation and transfer of photoexcited charge carrier and increase the specific surface area and the number of active sites is regarded as an effective strategy.In this study,Ti₃C₂ quantum dots were prepared and used to boost the photocatalytic activity of Bi₂O₃,and related mechanisms were studied.MXene（two-dimensional transition metal carbide）is a new type of graphene-like two-dimensional material and has been extensively studied due to the unique structure,fascinating electronic properties,abundant surface chemical terminations,good structural stability,and excellent light absorption ability.Thanks to these properties,MXene shows great potential as a co-catalyst to form a good synergistic catalytic effect with semiconductor photocatalysts.Compared with two-dimensional MXene nanosheets,adopting MXene quantum dots to construct composite photocatalysts can better exert the fascinating nature of MXene.Derived from 2D Ti₃C₂ single nanosheet,the Ti₃C₂ quantum dots（Ti₃C₂ QDs）inherit the excellent conductivity and light adsorption ability.But Ti₃C₂ QDs possess higher specific area and larger pore size than Ti₃C₂ nanosheets.In addition,due to the size effect,more surface Ti atoms are exposed,which are more suitable for photocatalytic pollutant degradation.In this study,Ti₃C₂ QDs were prepared by Ti₃C₂ nanosheets,and Ti₃C₂ QDs/Bi₂O₃composites with different content of Ti₃C₂ QDs were prepared by a hydrothermal method.The prepared samples were used for the photocatalytic removal of tetracycline（TC）.Exploring the boost effect and mechanism of Ti₃C₂ QDs as co-catalysts on the performance of the Bi₂O₃.Transmission electron microscopy（TEM）,Zeta particle size analysis and Photoluminescence excitation spectra（PL）showed that Ti₃C₂ QDs were successfully prepared with an average size of 3.96 nm.A series of characterizations showed that the Ti₃C₂ QDs/Bi₂O₃ composite was successfully prepared.The optimal Ti₃C₂ QDs/Bi₂O₃ composite can achieve 82%removal rate of TC under visible light irradiation within 1.5 hours,which is 5.85 times than that of pristine Bi₂O₃.In addition,the internal reasons for the improvement of the photocatalytic performance of composites were studied.The introduction of Ti₃C₂ QDs increased the visible light absorption capacity of the composite photocatalytic system.At the same time,Ti₃C₂QDs and Bi₂O₃ semiconductor formed a close contact,accelerated the separation of photogenerated carriers,and effectively inhibited the recombination of photogenerated electron-hole pairs.In addition,through nitrogen adsorption-desorption（BET）characterization calculations,the average pore size and specific surface area of the Ti₃C₂ QDs/Bi₂O₃ composite have been greatly improved,which increased the contact area between the material and the reactant,which can provide more active sites.This study proves that the great potential of Ti₃C₂ QDs as co-catalyst to improve the photocatalytic performance of semiconductors,and provides reference for the preparation of MXene quantum dots and their use in the field of photocatalysis.