Construction Of PbBiO₂Br-based Materials For Photocatalytic Organic Pollutants Removal

With the rapid development of economy and industrialization,the energy crisis and environmental pollution have become the key issues for human beings.Semiconductor photocatalytic technology,as an advanced oxidation technology,has potential application value in the fields of environmental restoration and new energy development.Designing photocatalysts with broad spectral response,large active specific surface area,high carrier separation efficiency,high quantum conversion rate,and excellent photocatalytic activity is the current research focus in the field of photocatalysis.Bismuth-based bimetallic oxyhalides are novel layered semiconductors photocatalytic material with adjustable band,wide spectral response and easy preparation.They show corresponding catalytic performance in the fields of photocatalytic degradation of organic pollutants,water decomposition and CO₂reduction.However,their catalytic activity are still low and cannot be commercialized.Therefore,effective strategies need to be explored to improve the photocatalytic performance of materials.In this paper,the main research object is bismuth-based bimetallic oxyhalide,PbBiO₂Br.By designing uniform porous microsphere structure;two-dimensional ordered mesoporous graphite phase carbon nitride?mpg-C₃N₄?,one-dimensional carbon nanotubes?CNT?,zero-dimensional carbon polymer quantum dots?CPDs?modified PbBiO₂Br heterostructure materials;rich oxygen defect ultra-thin atomic layer structure to effectively improve the photo-generated carrier separation efficiency of PbBiO₂Br-based materials,increase surface active sites,and thereby promote photocatalytic degradation performance of environmental organic pollutants?dye,antibiotics,endocrine disruptors,etc.?.The structure-activity relationship of enhanced photocatalytic performance of PbBiO₂Br-based materials was explored in detail,and the possible photocatalytic mechanism was concluded.The specific research content is as follows:In this paper,uniform porous PbBiO₂Br microspheres were first prepared with the ionic liquid[C₁₆mim]Br and polyvinylpyrrolidone?PVP?composite structure directing agent.Scanning and transmission electron microscopy confirmed that the uniform porous microspheres were successfully constructed.The results of nitrogen adsorption-desorption experiments show that the uniform porous structure significantly increases the specific surface area of PbBiO₂Br-based materials.The special porous structure is conducive to the multiple refraction and reflection of incident light,enhancing the utilization of sunlight,while optimizing the carrier separation efficiency and increasing the quantum conversion efficiency of sunlight,thereby significantly improving the photocatalytic degradation of organics in the environment performance of pollutants?colorless antibiotic ciprofloxacin?CIP?,endocrine disruptor bisphenol A?BPA?and colored dyes rhodamine?RhB?,methylene blue?MB??.Electron spin resonance?ESR?and free-radical capture experiments revealed that the main active species in the photocatalytic degradation process were superoxide radicals?·O₂^-?and holes?h⁺?.A possible photocatalytic mechanism was proposed.A mesoporous graphite carbonitride-modified porous PbBiO₂Br microsphere?mpg-C₃N₄/PbBiO₂Br?composite photocatalyst was successfully prepared by solvothermal method.SEM and TEM images show the mpg-C₃N₄ was evenly distributed on the surface of porous PbBiO₂Br microspheres.Due to energy band matching,the introduced mpg-C₃N₄ can effectively improve the migration and separation efficiency of photogenerated carriers in composites.Under visible light irradiation,compared with the pure PbBiO₂Br,the mpg-C₃N₄/PbBiO₂Br composite photocatalyst showed more excellent degradation activity for CIP,BPA and tetracycline hydrochloride?TC?as target pollutants.And the 3 wt%mpg-C₃N₄/PbBiO₂Br composite shows the highest photocatalytic performance.The main active species of photocatalyst in the photocatalytic process were identified as·O₂^-and h⁺.In addition,based on the corresponding band structure of mpg-C₃N₄ and PbBiO₂Br materials,a possible photocatalytic mechanism of mpg-C₃N₄/PbBiO₂Br composite catalyst was proposed.In the reactive ionic liquid system,the CNT/PbBiO₂Br composite photocatalyst was prepared by a solvothermal method.CNT are uniformly distributed on the surface of PbBiO₂Br ultrathin nanosheets.Under ultraviolet,visible,and?>580 nm,the prepared CNT/PbBiO₂Br composite exhibited enhanced photodegradation efficiency for the antibiotic CIP.The introduction of CNT enhances the light absorption of the material,reduces the carrier recombination rate and acts as a separation center for photo-generated electrons and an active site for pollutant degradation.Compared with the monomer PbBiO₂Br,the molecular oxygen activation capacity of the CNT/PbBiO₂Br composite photocatalyst is significantly improved.Electron spin resonance and active species capture experiments show that superoxide radicals and holes are the main active species in the photocatalytic process,and a possible photocatalytic mechanism is proposed.The carbonized polymer dots?CPDs?/PbBiO₂Br heterojunction photocatalytic materials have been designed from sacrificial ionic liquids.On the one hand,ionic liquids act as template and reaction source to induce the formation of PbBiO₂Br materials;on the other hand,they act as adhesives to anchor CPDs in situ on the surface of PbBiO₂Br materials under hydrogen bonding to construct composite photocatalysts.The introduction of CPDs not only effectively improves the migration and separation efficiency of photo-generated carriers of CPDs/PbBiO₂Br composites,but also increases the active specific surface area.Under ultraviolet,visible,and?>580 nm,the degradation antibiotic CIP performance of CPDs/PbBiO₂Br composites has been significantly improved.In addition,without the sacrificial reagent and the photosensitizer,the CPDs/PbBiO₂Br composite exhibit improved photocatalytic performance for reducing CO₂ to CO.The introduction of CPDs optimizes the adsorption/desorption balance of the reactants/products on the surface of the material,such as increasing the CO₂ adsorption capacity,proton affinity and CO release capacity.The possible photocatalytic reaction mechanism was deduced by in-situ FT-IR spectroscopy.Ultrathin PbBiO₂Br atomic layer materials with different oxygen defect concentrations on the surface have been prepared by solvothermal method.The construction of ultra-thin rich oxygen defect structure facilitates the migration of photo-generated carriers from the bulk phase to the surface,reduces bulk-phase carrier recombination,and enriches photo-generated electrons on the surface for oxygen defects,effectively improving the lifetime of photo-generated electrons.Under visible light irradiation,with RhB as the target pollutant,compared with deficient oxygen vacancies PbBiO₂Br atomic layer and bulk PbBiO₂Br materials,the ultrathin PbBiO₂Br atomic layer materials with oxygen deficiency exhibit the best degradation activity.In addition,oxygen deficiency is also an effective active site for the enrichment and activation of CO₂ molecules.For this reason,the oxygen-deficient ultrathin PbBiO₂Br atomic layer material also exhibits the best photocatalytic CO₂ conversion efficiency.This paper focuses on the controllable preparation,energy band regulation,defect construction,optimization of carrier migration and separation efficiency,and enhancement of photocatalytic degradation of organic pollutants and CO₂ resource utilization in new bimetallic oxyhalide PbBiO₂Br-based materials.Combining experimental characterization and theoretical calculations,the structure-activity relationship between the microstructure adjustment and photocatalytic activity of the prepared PbBiO₂Br-based materials and the corresponding photocatalytic mechanism were explored.It provides a scientific basis for the research of bismuth-based bimetallic oxyhalides in the field of photocatalytic environmental remediation and energy conversion,which exhibit great significance for theoretical basic research and industrial application.