Study On Preparation Of Al₂O₃-based Nanocomposite Materials And Their Photocatalytic Performance

In recent years,the developing of clean and sustainable energy and solving of growing problems of environmental pollution have attracted worldwide attention.Semiconductor photocatalytic technology converts solar energy into chemical energy at room temperature,meaning great significance for both solving energy shortage and environmental pollution problems.It is well-known that graphite phase carbon nitride is non-toxic and chemically stable while it has a low specific surface area and narrow response to visible light,and that silver halide has a good photoresponse to visible light despite photosensitivity apart from easy agglomeration,which therefore limits their utilizationin practice.Thus,in this thesis,Al₂O₃ microspheres with large specific surface area and high stabilityare used as substrate to combine g-C₃N₄ and AgX（AgCl、AgBr、AgI）to prepare multi-element photocatalytic composites,which exhibit enhanced photocatalytic activity because of the improved dispersibility and specific surface area of the g-C₃N₄ and AgX.Moreover,the defect sites of Al₂O₃ could capture electrons so as to facilitate the efficiency of separation and migration of electron-hole pairs from the composite for photocatalysis.The specific research content is as follows:（1）The g-C₃N₄/Al₂O₃ composite material was prepared by calcination method.This composite has superior photoelectrochemical properties and decent performances of photocatalytic degradation of organic pollution.Thereis a stable heterojunction between g-C₃N₄ and Al₂O₃.And the large specific surface of Al₂O₃ provides more defect sites that is beneficial for the capture of the photo-induced electrons from g-C₃N₄ and thereby facilitates effective separation and transport of charge carriers.（2）The Ag/g-C₃N₄/Al₂O₃ composites were prepared by calcination and reduction method.The resultant composites have extraordinary property of photoelectrochemistry,ability of photoelectrolysis of water splitting and degradation of dyes,which are attributed to the large specific surface area and surface defect sites of Al₂O₃ and the high photoactivity of g-C₃N₄ in visible light.Moreover,the introduction of Ag that increases the visible light absorption range of the material and greatly promotes the separation of charge carriers and their transfer.（3）The AgX/Ag/Al₂O₃ composites were synthetized by photoreduction and chemical precipitation.The obtained material has excellent photocatalytic degradation of dyes,mainly because the dispersibility and specific surface area of AgX were improved due to the large surface area and defect sites of Al₂O₃.Futhermore,the mighty surface plasmon resonance of Ag nanoparticles can enhance the absorption of visible light,and facilitate the separation and migration of photogenerated electron-hole pairs.