Preparation And Photocatalytic Properties Of Graphene Modified P-Biocl/n-Bi₂S₃ Heterojunction Photocatalyst

Photocatalytic degradation is a green pollution purification technology that has gradually emerged in recent years.It can convert solar energy into chemical energy,and has good stability and reusability.It is the best choice for solving environmental and energy problems.The new semiconductor photocatalyst BiOCl is the focus of research in the field of photocatalysis at present.Its unique layered structure and indirect optical transition mode can improve the recombination of photogenerated carriers in photocatalytic materials,but the recombination of most photogenerated electrons and holes It still exists,and at the same time,the existence of the wide band gap makes it unable to respond to visible light,the utilization efficiency of solar energy is very low,and there is still much room for improvement of photocatalytic performance.Based on the basic properties of BiOCl,this paper proposes to form a"heterojunction"between BiOCl and narrow-bandgap semiconductor Bi₂S₃,and the reduction of graphene oxide has the advantages of"high conductivity,high carrier mobility and large specific surface area".Therefore,the graphene oxide is further doped on the basis of the binary heterojunction material,and the modification of BiOCl is further deepened,the photocarrier carrier separation is further promoted,and the visible light photocatalytic efficiency is fully improved.BiOCl was prepared by one-step hydrothermal method.Then,graphene oxide-doped Bi₂S₃/BiOCl-rGO was synthesized on the basis of preparation of heterojunction materials.In order to investigate the morphology,light absorption and photocatalytic activity of the composite photocatalyst,the paper used various characterization methods and obtained the following conclusions:（1）The composite material Bi₂S₃/BiOCl-rGO consists of a band-shaped particle BiOCl and a sheet Bi₂S₃ attached thereto.It can be observed that BiOCl has a band-like morphology with an average diameter of about 0.5 um and a length of about 5 um.Since the unique structure of the heterojunction has strong photogenerated electron and carrier separation ability,the Bi₂S₃/BiOCl-rGO heterojunction material combined with Bi₂S₃ exhibits a distinct absorption band in the visible wavelength range of 350-600 nm.Extending the visible light response range of BiOCl to about 630 nm significantly improved the light absorption capacity of BiOCl.（2）Graphene oxide as a modified material did not change the morphology and crystal form of the p-BiOCl/n-Bi₂S₃-rGO heterojunction after incorporation.The energy spectrum analysis confirmed that the graphene oxide was successfully prepared and uniformly distributed in the heterojunction material.Under 450 nm visible light excitation,the doping of graphene extends the visible light response range of BiOCl to650 nm,and the light absorption capacity is also significantly enhanced.The rGO layer and the ribbon binary composite are closely embedded,but the TEM image shows that the morphology of the composite does not change.It is found from the TEM image that Bi₂S₃ and BiOCl are closely linked and difficult to distinguish.They are closely intertwined during the hydrothermal reaction,which is supposed to be caused by anion exchange between Cl^-and S^2-.（3）The four influencing factors of photocatalytic degradation of TBBPA were investigated by the photocatalytic degradation of TBBPA by BiOCl,Bi₂S₃/BiOCl and p-BiOCl/n-Bi₂S₃-rGO photocatalysts:catalyst dosage m,initial concentration of TBBPA to be degraded C₀,light intensity E,reaction system pH.Catalyst dosage experiments showed that 0.3g/L was the optimal photocatalyst dosage after 8h reaction,and the optimal degradation effect could not be obtained above or below 0.3g.The substrate concentration is inversely proportional to the degradation effect of the TBBPA solution.Degradation data at different pHs indicate a higher photocatalytic reaction rate when the pH is lower or higher.When the light intensity increased,the photocatalysts BiOCl,Bi₂S₃/BiOCl,p-BiOCl/n-Bi₂S₃-rGO gradually increased the degradation rate of TBBPA.The illumination intensity is enhanced,the quantum efficiency of the catalyst is gradually enhanced,and the photocatalytic reaction rate is accelerated.The photocatalytic activity of BiOCl,Bi₂S₃/BiOCl and p-BiOCl/n-Bi₂S₃-rGO was compared.p-BiOCl/n-Bi₂S₃-rGO had the highest degradation rate of TBBPA,while BiOCl had the lowest degradation rate.（4）The degradation of TBBPA by p-BiOCl/n-Bi₂S₃-rGO in the presence of different free radicals showed that the system with·O₂^-and·OH coexisted had a higher degradation rate of contaminants than the solution containing O₂^-or·OH.This indicates that during the degradation of tetrabromobisphenol A,the active particles·OH and·O₂^-have a certain contribution rate in the degradation reaction.The intermediate products of the TBBPA degradation process were tested,and six products were mainly found.The kinetics of the initial substrate concentration level of TBBPA and the degradation experimental data were analyzed and the kinetics were fitted.The results showed that the reaction parameters showed a good linear relationship,indicating that the TBBPA photolysis reaction belongs to the first-order kinetic reaction.