Preparation Of TiO₂ Composite Catalyst And The Properties Of Photocatalytic Degradation Of Organic Pollutants

Ecological and energy issues are the two biggest issues in the world.Solar-assisted semiconductor photocatalysis is a potential and sustainable technology to address these problems,using free solar energy to generate clean energy and remove organic pollutants from industrial wastewater that pose a significant threat to environmental safety and human health.Currently,various semiconductors are used as potential effective photocatalysts for environmental pollution control.It is noteworthy that titanium dioxide has good environmental compatibility and good activity,and has the advantages of low cost and long-term stability compared with other semiconductors in the control of environmental pollutants.However,the low energy efficiency of TiO₂is an important issue limiting its practical application.This is because it exhibits a higher band gap energy（3.2 e V）and can only be excited by a lower wavelength UV light irradiation.Further,the 3-5%of the initial sunlight that reaches the earth’s surface can only be absorbed at a wavelength of less than 400nanometers.Therefore,the visible-light photocatalysis is not very efficient.Moreover,the reorganization of the resulting electron-hole pair also reduces its quantum efficiency.These defects are caused by the properties of TiO₂it self,and it can only be modified by some methods to improve its photocatalytic properties.This work mainly improves the visible light absorption capacity of titanium dioxide by depositing the precious metal or reducing the band gap by elemental doping,and then the photocatalytic performance is further improved by coupling the effective heterojunction with the new non-metallic photocatalyst material g-C₃N₄（CN）.The main research contents are as follows:（1）A rectangular titanium dioxide nanosheets（TNS）are synthesized by hydrothermal method.Through the deposition technology of nanoparticles in situ and programmed calcination in N₂atmosphere,a good TNSs@Au crystal interface at the edge position,which can greatly expand the visible light absorption wavelength,which is attributed to the gold particles deposited on the surface plasmon resonance（LSPR）effect at the Au/TiO₂interface and the close interface contact between gold nanoparticles and titanium dioxide nanosheets can greatly improve the separation efficiency of photogenerated carriers.Then,a TNSs@Au/g-C₃N₄ternary Z photocatalyst based on 2D/0D/2D material was constructed by combining g-C₃N₄thin layer coverage at the Au/TiO₂interface,which successfully coupled the cut plane junction and heterojunction,while achieving efficient charge separation,redox capacity and large reaction surface area.（2）On the basis of the previously synthesized titanium dioxide nanosheets,the introduction of N and S element doping can adjust the TiO₂band gap to enhance the visible light absorption to improve its photocatalytic activity under visible light.Finally,the modified titanium dioxide nanosheets NS-TiO₂and g-C₃N₄thin layer were combined to construct an effective heterojunction to form CN/NS-TiO₂composites,which further improves the photocatalytic performance and maintains the photocatalytic stability.Moreover,replacing the precious metal deposition greatly reduces the cost of CN/NS-TiO₂nanocomposites more practical.