| Semiconductor photocatalysts can efficiently use sunlight to degrade organic pollutants and show great application prospects in solving environmental pollution issues.With continuous exploration and discovery in recent years,the Sillén-Auivillius type bismuth-based photocatalyst Bi4NbO8X（X=Cl,Br）has a suitable band gap,excellent physical and chemical properties and photocatalytic activity,among many studied semiconductor,attracting extensive attention from scholars.In this paper,Bi4NbO8Br and Bi4NbO8Cl photocatalysts were synthesized,and their structure and optical properties were characterized by a variety of analysis and testing techniques.Different types of organic pollutants were degraded,the photocatalytic activity of the catalyst was evaluated,and the mechanism of enhanced photocatalytic performance was explored through further experiments.The main research of this thesis includes:1.The Bi4NbO8Br material with oxygen-rich vacancies was prepared by the solution combustion method,and then Pt nanoparticles were loaded on the surface of the Bi4NbO8Br material by the in-situ chemical reduction method to construct a new Pt/Bi4NbO8Br composite photocatalytic system.Through research,it is found that the Pt nanoparticles loaded on the interface form the Mott-Schottky effect,which induces the transfer of photogenerated electrons,thereby realizing the rapid separation of photogenerated carriers.In addition,the metal-support interaction between the Pt nanoparticles and the Bi4NbO8Br sheet reduces the formation energy of oxygen vacancies,thereby promoting oxygen activation to generate more oxygen vacancies.Through the photocatalytic mechanism test,it is found that in the degradation catalysis process,photogenerated holes play a major role,while superoxide radicals play a minor role.Compared with Bi4NbO8Br,Pt/Bi4NbO8Br shows good photocatalytic activity to all organic pollutants.2.The flaky Bi4NbO8Cl material with regular morphology was prepared by the molten salt method,and the non-noble metal Bi in-situ loaded Bi4NbO8Cl composite photocatalytic system was constructed by the in-situ solvothermal method.Without the additional introduction of Bi source,only the solvent was used.The[Bi2O2]block released during the thermal reaction serves as the precursor of Bi nanoparticles and increases the generation of oxygen vacancies.Since the metal Bi has a larger work function similar to that of the metal Ag,a Schottky barrier can be formed at the Bi/Bi4NbO8Cl interface,thereby accelerating the separation of photogenerated carriers in the semiconductor and providing more holes for the decomposition of organics.In addition,oxygen vacancies assist in the activation of oxygen adsorbed on the catalyst surface to generate superoxide radicals,promote photo-generated electron consumption,and leave more photo-generated holes in the Bi4NbO8Cl valence band,thereby realizing the Bi/Bi4NbO8Cl photocatalyst to a variety of organic pollution The photocatalytic performance of the product is enhanced.3.The heterostructure Ag2S/Bi4NbO8Cl composite photocatalyst was prepared by a simple chemical precipitation method at room temperature.Through morphological characterization,it can be observed that the Ag2S/Bi4NbO8Cl composite photocatalyst has a cookie-like structure.Compared with pure Bi4NbO8Cl and Ag2S,the photocatalytic degradation ability of Ag2S/Bi4NbO8Cl is significantly enhanced under visible light and near-infrared light,thanks to the enhanced light absorption intensity of the composite photocatalyst under visible-near-infrared light and the expanded light response range promotes the rapid separation and utilization of photo-generated carriers.It can be seen from the degradation performance test that the Ag2S/Bi4NbO8Cl composite photocatalyst exhibits a good degradation effect regardless of whether it is under visible light or near-infrared light. |
