Preparation Of Two-dimensional MXene/bismuth-based Nanocomposites And Their Visible Light Catalysis Performance Study

Environmental pollution and energy shortage are two major problems that humans have long been concerned about.The development of efficient and stable visible light catalytic materials has become a research hotspot in recent years.As a new type of photocatalytic material,bismuth oxyhalide has attracted wide attention from researchers due to its unique layered structure.Based on this,in this study,two highly efficient and stable composite photocatalytic materials were prepared using self-made Ti₃C₂ with lamellar structure as a co-catalyst;using BiOBr,a bismuth-based visible light catalytic material as a template;two highly efficient and stable composite photocatalytic materials were prepared.The relationship between preparation methods and performance was discussed,and the catalytic degradation of dyes,reduction of Cr（Ⅵ）,and hydrogen production under visible light were studied,the photocatalytic degradation mechanism has been further studied.The research content of this paper is briefly described as follows:（1）The preparation conditions of monolithic Ti₃C₂ nanosheets under the HCl/LiF system were optimized by"Ultrasonic And Stirring",and the influence of etching time and ultrasonic power was investigated by the single factor method.The results show that on the basis of the HCl/LiF etching system,with a controlled temperature of 50±5°C,an ultrasonic power of400W,and ethanol as the intercalant,a monolithic layer of Ti₃C₂ with large size and low defects can be prepared in a relatively short time.The sheet has a sheet size greater than 5μm,and the prepared material has a high purity without obvious impurities.（2）Using octanol as the solvent,the BiOBr/Ti₃C₂ composite photocatalytic material（OBT）with controllable structure and size was constructed by the non-good solvothermal method.The single factor method discussed the influence of solvothermal conditions（temperature,time）and the amount of Ti₃C₂ on the composition,morphology and characteristics of OBT.Using Rh B visible-light catalytic degradation to evaluate OBT visible-light response activity,and the photocatalytic mechanism of OBT is analyzed.The results show that BiOBr prepared with n-octanol as a solvent has a loose curd structure with a diameter of less than 5μm.The optimal preparation conditions are solvothermal temperature of 120℃,time of 12h,and the amount of co-catalyst Ti₃C₂ added is 0.3g.Photocatalytic degradation experiments show that 10 mg of OBT still has a good photocatalytic effect on the Rh B dye solution under the conditions of pH=7 and a concentration of 100 mg/L.Research on the photocatalytic degradation mechanism shows that the excellent photocatalytic performance benefits from its enhanced photocatalytic performance,visible light absorption performance and good electron transfer performance.Capture agent experiments and paramagnetic electron spectroscopy experiments show that superoxide radicals（·O₂^-）are the main active species of OBT.（3）Using anhydrous bismuth nitrate and potassium bromide as raw materials,NaOH as the pH regulator,Bi₂₄O₃₁Br₁₀ is grown in-situ between the layers of BiOBr curds to construct a bismuth-rich photocatalytic material Bi₂₄O₃₁Br₁₀/BiOBr（BOB）.The single factor method discussed the influence of pH and calcination time on the morphology and properties of the material.At the same time,using the lamellar layer Ti₃C₂prepared above as the electron acceptor,the Bi₂₄O₃₁Br₁₀/BiOBr/Ti₃C₂ ternary composite photocatalytic material（BOBT）was prepared,and its microscopic morphology and photoelectrochemical performance were studied by XRD,XPS and other characterization techniques.The photocatalytic performance was further verified by dye degradation,Cr（Ⅵ）reduction,and photocatalytic hydrogen production experiments.The results show that when pH=8,Bi/Br=1/1,and the calcination temperature is 400℃,BOBT has the best crystal structure,and the bulbous structure gradually becomes loose,with a diameter of about 5μm,which has the best visible light absorption.The electrochemical responsiveness,degradation experiments show that BOBT has a good photocatalytic effect on different concentrations of Rh B,MO,TBO simulated dye solutions,and at the same time,20 mg BOBT has close to 100%for Cr（Ⅵ）solutions below20mg/L,the reducibility and the concentration after degradation reached the limit value in the national standard.The photocatalytic hydrogen production experiment showed that the hydrogen production of the prepared BOB and BOBT were increased by about 2.30 and 3.51times compared with the pure phase BiOBr without adding Pt as a co-catalyst.The research in this paper provides some basic research for the construction of two-dimensional MXene/bismuth-based heterojunction materials.