Synthesis And Enhanced Photocatalytic Performance Evaluation Of PbBiO₂Cl Based Materials

Photocatalysis is considered to be one of the most promising technologies to solve the problems of energy shortage and environmental pollution that threaten the development of human society.Photocatalytic technology has a broad application prospect in the fields of water decomposition,hydrogen production,CO₂ reduction,organic synthesis,sterilization,environmental governanceand so on.In addition,photocatalytic degradation can convert organic pollutants directly into carbon dioxide,water and non-toxic products without secondary pollution.It has been regarded as a potential environmental remediation method and has attracted more and more attention.At present,one of the focuses of photocatalytic research is to develop photocatalytic materials that are economical,effective,simple and easy to obtain,excellent performance and stable activity,and more efficient photocatalysts are expected to be prepared.In this thesis,a novel and highly effective PbBiO₂Cl photocatalytic material with controllable morphology was prepared by using reactive ionic liquids and surfactants.The PbBiO₂Cl photocatalytic materials with controllable morphology were synthesized by a simple solvothermal method.At the same time,the optical absorption range and photocatalytic activity were regulated by combination of carbon quantum dots?CQDs?and graphitic carbon nitride?g-C₃N₄?.In addition,the photocatalytic activity of the prepared materials was investigated by using the refractory and colourless pollutants as models,and the morphology,structure,composition and photoelectric properties of the materials were analyzed by various characterization methods so as to explore the possible photocatalytic mechanism.The specific research contents are as follows:Novel perovskite-like PbBiO₂Cl materials with hollow and porous sphere-like structures were prepared by the interaction of polyvinyl pyrrolidone?PVP?and reactive ionic liquid 1-hexadecyl-3-methylimidazoliumchlorine([C₁₆mim]Cl).TEM were used to characterize the hollow-porous structure formed by the double regulation of the ionic liquid and PVP.The hollow-porous PbBiO₂Cl photocatalysts showed excellent photocatalytic properties during the degradation of the colorless antibiotic ciprofloxacin?CIP?and tetracycline?TC?under visible light irradiation.The enhanced photocatalytic properties of PbBi O₂Cl materials were mainly derived from their porous and hollow structures.This special structure could increase the specific surface area and accelerate the interfacial charge separation.Moreover,based on the analysis of XPS valence spectra,electron spin resonance?ESR?spectra and free radical trapping experiments,the main active species were determined to be holes and superoxide radicals during the photocatalytic degradation process.On the basis of the PbBiO₂Cl synthesis above,CQDs/PbBiO₂Cl composite was formed by modifying the zero-dimensional nonmetallic CQDs onto the surface of PbBiO₂Cl microspheres.The composites with different contents were obtained by controlling the proportion of CQDs in the synthesis process.The structure,morphology,surface properties,optical properties,electronic structure and photocatalytic properties of the composites were studied in detail.The results showed that the photocatalytic activity of CQDs/PbBi O₂Cl composite was significantly higher than that of pure PbBiO₂Cl in the degradation of rhodamine B?RhB?and CIP.At the same time,0.5 wt%CQDs/PbBi O₂Cl composite exhibited the best photocatalytic performance.The results of electron spin resonance?ESR?and active species capture experiments showed that the main active species in photocatalytic degradation were holes and superoxide free radical under visible light irradiation.As the center of photocatalytic reaction,CQDs could rapidly transfer photogenerated electrons from PbBiO₂Cl,which could effectively separate electron-hole pairs and enhance photocatalytic activity.In addition,g-C₃N₄/PbBiO₂Cl composites were formed by introducing few-layer g-C₃N₄ in order to further enhance the photocatalytic activity of pure PbBiO₂Cl materials.Various techniques have been applied to discuss physicochemical properties of g-C₃N₄/PbBiO₂Cl composite such as XRD,SEM,TEM,FT-IR,UV-vis,BET,DRS and ESR.The synthesized photocatalysts exhibited outstandingly enhanced photocatalytic activity compared with that of pure PbBiO₂Cl material under visible light.Furthermore,the optimal mass ratio of the g-C₃N₄ to PbBiO₂Cl was 3 wt%.The colorless CIP and colored RhB were chosen as model pollutant to evaluate the as-prepared g-C₃N₄/PbBiO₂Cl photocatalyst.The high degradation efficiency was due to the interfacial interaction between g-C₃N₄ and PbBiO₂Cl,i.e.an appropriate distribution of PbBiO₂Cl microsphere on the surface of g-C₃N₄ and an improved separation rate of photogenerated electron-hole pairs.The enhanced photocatalytic activity mechanism was also investigated using radical trapping experiments,electron spin resonance?ESR?,photogenerated current densities and electrochemical impedance spectroscopy?EIS?.Radical trapping experiments and electron spin resonance tests both proved that the g-C₃N₄/PbBiO₂Cl composites can generate more·O^2-and h⁺for photocatalytic degradation.