Preparation And Performance Research For Bi₃O₄Cl-based Nanocomposite Photocatalysts

With rapid economic development,the discharge of industrial wastewater and domestic sewage has led to the pollution of water bodies.Photocatalytic semiconductor technology is considered a promising way to solve the problem of water pollution due to its use of clean and renewable solar energy.In the exploration of semiconductor materials,bismuth-based photocatalytic materials have received increasing attention due to their suitable band gap and excellent physicochemical properties.This paper is based on Bi₃O₄Cl prepared by solid-phase method to improve photocatalytic performance by constructing heterojunctions of Bi₃O₄Cl with other bismuth-based semiconductor materials.This approach allows for improved sunlight utilisation and more efficient separation and migration of photogenerated carriers,resulting in better degradation of organic pollutants in aqueous solutions.The main researches in this thesis are as follows:（1）Bi₃O₄Cl/Bi₄Nb O₈Cl Z-Scheme heterojunction catalysts for enhanced photocatalytic degradation of organic pollutants:Bi₃O₄Cl and Bi₄Nb O₈Cl are prepared by solid-phase method respectively,and Bi₃O₄Cl/Bi₄Nb O₈Cl heterojunction catalysts are obtained by grinding and calcining different ratios of Bi₃O₄Cl and Bi₄Nb O₈Cl.X-ray Diffraction（XRD）,Scanning Electron Microscopy（SEM）and Transmission Electron Microscopy（TEM）characterize the morphology and physical phases of the materials,demonstrating the formation of heterojunction composites.The photocatalytic experiments using Ciprofloxacin（CIP）and Bisphenol A（BPA）as target degradants showed that the degradation performance of Bi₃O₄Cl/Bi₄Nb O₈Cl photocatalyst was greatly improved.UV-Vis diffuse reflectance spectroscopy（DRS）and photoelectrochemistry tests showed a narrower band gap and a faster carrier migration rate in the composite.Z-scheme heterostructure is formed between Bi₃O₄Cl and Bi₄Nb O₈Cl,which inhibits carrier complexation and allows more holes and superoxide radicals to participate in the degradation process.（2）In situ construction and photocatalytic properties of Bi/Bi OCl/Bi₃O₄Cl heterostructures:Bi/Bi OCl/Bi₃O₄Cl ternary heterojunction photocatalysts are synthesised by a solvothermal method using Bi₃O₄Cl as raw material.A series of X%Bi/Bi OCl/Bi₃O₄Cl heterojunction photocatalysts are prepared by modulating the bismuth source.Rhodamine B（Rh B）and Ciprofloxacin（CIP）were used as target pollutants to study their catalytic performance.X-ray Photoelectron Spectroscopy（XPS）showed that the introduction of Bi metal particles has changed the chemical state of the photocatalytic material.Transmission Electron Microscopy（TEM）and nitrogen adsorption desorption tests showed that the production of large amounts of Bi OCl and Bi nanoparticles increased the specific surface area of the composites and that 7%Bi/Bi OCl/Bi₃O₄Cl had more micropores.Photoluminescence（PL）and electrochemical experiments had demonstrated increased carrier transfer rates and significantly reduced complexation rates in Bi/Bi OCl/Bi₃O₄Cl.Bi/Bi OCl/Bi₃O₄Cl heterojunction photocatalysts have a much higher photocatalytic degradation activity due to the heterogeneous structure and the synergistic effect of Bi nanoparticles.