Research On Photocatalysis Properties And Mechanism Of Au/TiO₂ Materials

Facing with the increasingly serious water pollution problems,semiconductor photocatalyst technology can be directly used to convert solar energy into the chemical energy which is required for degradation,so it has been a highly efficient and clean sewage treatment method.Among many semiconductor materials,TiO₂nanomaterial,as a photocatalyst for sewage treatment,has shown great potential,but its wide bandgap structure determines that it can only be excited by ultraviolet rays,as a result,it wastes the main visible part of the sunlight.Therefore,Localized Surface Plasmonic Resonance effect?LSPR?of the metal nanoparticles by loading precious metal onto TiO₂ is a method to enhance the absorption efficiency of the photocatalytic material in the visible light band and improve the separation rate of the photo-generated electron-hole pairs,which is very important to promote and develop photocatalytic materials.In this paper,Au/TiO₂ powder and thin film materials with different Au loading amount have been successfully prepared and characterized by different methods.The most optimal loading parameter is obtained by studying the photocatalytic efficiency.Measuring the charge migration of Au/TiO₂ film under different illumination conditions by using Kelvin Probe Force Microscopy?KPFM?,we obtain the charge migration process of TiO₂ and Au,which reveals the direct evidence that the Localized Surface Plasmon Resonance?LSPR?of metal nanoparticles has enhanced photocatalytic performance.The specific tasks of study are as follows:The Au/TiO₂ powders with different Au loading amount are synthesized by hydrothermal method.The characterization of Scanning Electron Microscopy?SEM?and Transmission Electron Microscopy?TEM?show that the size of Au particles and TiO₂ respectively was 10 nm and 23 nm.The X-Ray Diffraction?XRD?images show that the content ratio of anatase and rutile is 4:1 in TiO₂ samples.The UV-Vis Diffuse Reflectance Spectroscopy?UV-Vis DRS?show that the absorption range of Au/TiO₂ is extended to the visible light band.The results of photocatalysis experiment show that photocatalytic degradation rate of Au/TiO₂ with the mass fraction of 0.5%is 15%higher than that of pure TiO₂,and it can reach 92%after reacting for 30 min.In order to solve the uneasy recovery problem of powder catalyst materials in the practical application,Au/TiO₂ film with different Au loading amount are synthesized by photoreduction method.Scanning Electron Microscopy?SEM?and Diffuse Reflectance Spectroscopy?DRS?results show that the morphology of Au-NPs is clavate firstly,and then change into spherical or island-like structure distribution as the growth time increasing.The photocatalytic experiments results show that the Localized Surface Plasmonic Resonance?LSPR?effect of metal nanoparticles can significantly improve the photocatalytic efficiency.Compared with TiO₂ film,the photocatalytic degradation rate of Au/TiO₂ film is 20%higher than that of pure TiO₂film,which can reach 58%after reacting for 3h.By setting up a Kelvin Probe Force Microscope?KPFM?test platform based on Atomic Force Microscopy?AFM?,we study the enhancement mechanism about photocatalytic performance of Au/TiO₂ film.The same sample area is tested under different illumination conditions to study the photoinduced charge separation at Au/TiO₂ interface,and then physical image of enhanced photocatalytic performance by LSPR effect can be obtained directly.