Research Of Enhanced Photocatalytic Reaction System Based On Photonic Crystal

Photocatalytic reactions have important practical value for solving the growing environmental and energy problems.Semiconductor photocatalysts are the focus of the research on photocatalytic reactions.A large number of studies have shown that enhancing light absorption,accelerating the separation of electron-hole pairs and increasing surface reaction activity are effective strategies for enhancing photocatalytic reaction activity.And improving the light harvesting efficiency is most widely used.Photonic crystals have the photonic bandgap（PBG）and can effectively reflect incident light with specific energy.It is particularly suitable for the photocatalyst carrier because it can promote multiple absorption and utilization of incident light.It is also suitable as a photocatalyst to directly catalyze the photo-reaction due to the slow photon effect which can slow down the photon velocity and enhance the capture of photons by the photocatalysts.Based on the unique ability of controlling photons by photonic crystal,we will develop the enhanced photocatalytic reaction system based on photonic crystals,explore the structure-activity relationship between the photonic crystal structure and photocatalytic activity,and lay the foundation of photonic crystal materials’ application in photocatalysis.In the second chapter,photonic crystal thin films were prepared by spin-coating and in-situ photopolymerization,and CdS quantum dots were loaded on the surface to prepare CdS/SiO2-ETPTA supported thin-film photocatalyst.The catalytic experiments show that the photocatalytic reaction rate could be enhanced by increasing the reflection intensity of PC films and matching the photonic band gap of PC with the electronic bandgap of photocatalyst.Then we prove that the photonic crystal films can provide additional incident light for the photocatalyst through reflection process,promote light absorption of the catalysts,thereby increasing photocatalytic activity.Related experiments have also determined specific methods for improving the activity of photocatalysts,such as controlling the thickness of CdS layer,band gap matching,and compositing metal thin layer.Compared with dispersed photocatalysts,the photonic crystal supported thin-film catalyst has advantages of high stability,easy separation,great recyclability,broad selection of catalysts.In addition,it can be well compatible with existing thin film preparation technologies to utilize solar energy for the various green processes.In the third chapter,the inverse opal TiO₂（TiO₂IO）photocatalysts（anatase）with ordered pore structure were prepared by using polystyrene（PS）particles as template,and used to the photocatalytic reaction of nitrobenzene hydrogenation.By comparing TiO₂ with disordered pore structure and nonporous TiO₂,the catalytic reaction due to itsIO TiO₂ can enhance the conversion and selectivity of the catalytic reaction due to its large specific surface area and slow photon effect.When incident light irradiating on a photocatalyst with a photonic crystal structure,photon propagation speed inside the semiconductor slows due to the slow photon effect,and this part of light can be reused by the semiconductor.The process can accelerate the photo-electron excitation rate and enhance the catalytic activity.Thereby we can control the photonic bandgap to improve the catalytic activity.The thin-film photocatalyst has the advantages of great cycling stability and high separation efficiency.It achieves the organic reaction successfully under mild reaction conditions without reduced gas,metal-free,low temperature and pressure.This work has extended the application of photonic crystals to organic reactions.