Study On Preparation And Performance Of BiOCl Visible Light-responsive Composite Photocatalyst

BiOCl is a new type of bismuth-based semiconductor photocatalytic material that is non-toxic and stable in physical and chemical properties.Due to its unique layered structure,it has better degradation activity than Ti O₂ photocatalysts under ultraviolet radiation.However,BiOCl and Ti O₂ have a similar forbidden band width（3.19～3.44 e V）,and have the disadvantages of poor photocatalytic performance and narrow light absorption range.Therefore,this paper takes BiOCl as the main research object,constructing solid solution structure and designing heterojunction structure to improve its photocatalytic activity through composition control and structure control.X-ray diffraction（XRD）,scanning electron microscopy（SEM）,UV-visible diffuse reflection（UV-Vis DRS）,transient current response（IT）and electrochemical impedance（EIS）were used to analyze the structure,morphology and photogenerated charge transfer characteristics of the prepared samples.The photocatalytic activity of the prepared materials was evaluated by a series of photocatalytic degradation experiments and active species trapping experiments.This study provides a new way to further develop a highly active photocatalytic system that can effectively treat pollutants.The main research contents are as follows:（1）Taking BiOCl/Br solid solution as the research object,the core-shell BiOCl/Br solid solution nano-photocatalyst was synthesized by one-step self-assembly method under mild water bath conditions.The influence of the addition of Br^-on the crystal structure,morphology,specific surface area,light absorption performance and photocatalytic degradation of MO of BiOCl was discussed.The results showed that by adjusting the surface charge of BiOCl and using electrostatic adsorption,Br^-doping into the crystal lattice of BiOCl to form a solid solution can effectively shorten the band gap of BiOCl and improve its photocatalytic activity.（2）Taking C₃N₄-DPY/BiOCl as the research object,the C₃N₄-DPY/BiOCl composite photocatalyst materials with different mass ratios were synthesized by the ultrasonic-assisted method with simple operation.After 2,6-diaminopyridine was doped into C₃N₄ as aπ-deficient conjugated pyridine ring,the specific surface area of C₃N₄ is effectively increased,the band gap is shortened,and the photocatalytic activity is improved.Select MO as the pollutant to evaluate the photocatalytic activity of the sample under visible light.The photocatalytic activity of the catalyst after BiOCl and modified C₃N₄ was significantly higher than that of pure BiOCl.In addition,different contents of C₃N₄-DPY combined with BiOCl have different effects on the degradation of MO,which may be related to the synergistic effect of C₃N₄-DPY and BiOCl.At the same time,the appropriate content of C₃N₄-DPY may facilitate its combination with BiOCl,creating more interfaces to improve the transfer of electrons and holes.Among them,the 0.5-C₃N₄-DPY/BiOCl composite photocatalyst has the most excellent photocatalytic activity.（3）Taking Bi@BiOCl/C₃N₄-DPY as the research object.First,Bi@BiOCl was synthesized by solvothermal method,and then the C₃N₄ was doped and modified by the lack ofπ-conjugated pyridine ring（2,6-diaminopyridine）.Finally,the modified carbon nitride and Bi@BiOCl nanoparticles were compounded by the co-precipitation method.In the photocatalytic degradation experiment,compared with other samples,Bi@BiOCl/C₃N₄-DPY heterojunction material exhibits excellent photocatalytic performance during the degradation of MO.Its high-efficiency photocatalysis is attributed to the photo-induced charge transfer in Z-Scheme Bi@BiOCl/C₃N₄-DPY,so that charge carriers have a high separation efficiency and high redox potential of photogenerated electrons and holes.In addition,Bi nanoparticles were used as the Z bridge in Bi@BiOCl/C₃N₄-DPY,which can accelerate the light-induced charge transfer in the Z-Scheme structure.