Preparation And Photocatalytic Properties Of The Titanium Dioxide Based Photocatalyst

With the advancement of science and technology and the development of society,the problem of environmental pollution has become increasingly prominent.In response to environmental problems,photocatalytic technology has become an effective method of pollution control due to its high-efficiency,non-toxic,low-cost,and recyclable advantages.Among many semiconductor photocatalysts,titanium dioxide（TiO₂）has the characteristics of high chemical stability,low price and non-toxicity,and has broader application prospects in the fields of environmental pollution control and new energy development.However,the band gap width of TiO₂ results in a narrow photoresponse range and high photogenerated carrier recombination rate.These shortcomings severely restrict the application of TiO₂ in the field of photocatalysis.Researchers modified TiO₂ by introducing precious metals and compound semiconductors to construct heterojunctions to make up for its own shortcomings and greatly improved the photocatalytic performance of TiO₂semiconductor materials.In this thesis,by depositing silver nanoparticles（AgNPs）and composite graphite phase carbon nitride（g-C₃N₄）,respectively,to explore their effects on the photocatalytic performance of TiO₂.Through X-ray diffraction（XRD）,scanning electron microscope（SEM）,X-ray photoelectron spectroscopy（XPS）,ultraviolet-visible diffuse reflectance absorption spectroscopy（UV-Vis DRS）,fluorescence emission spectroscopy（PL）and other characterization methods.Study its basic structural features and photophysical properties;and analyze the photoelectric response characteristics of the catalyst samples through electrochemistry.At the same time,combined with the degradation test of rhodamine B（Rh B）,phenol and methyl orange（MO）organic dyes,the photocatalytic activity of the TiO₂-based composite material system was preliminarily studied.The specific content is as follows:（1）Prepare micro-spherical nano-TiO₂ particles by hydrothermal method,load AgNPs on the surface of the catalyst by chemical reduction method,utilize the local surface plasmon resonance effect（LSPR）of AgNPs and the heterojunction structure formed with TiO₂.It not only enhances the light absorption capacity of the catalyst and broadens its light absorption range,but also reduces the recombination of photogenerated electrons and holes,thereby realizing the efficient degradation of Rh B and phenol.By further optimizing the loading of AgNPs,the catalyst with 3%Ag content（3%Ag/TiO₂）exhibits the best catalytic activity under simulated sunlight radiation,and the degradation efficiency of 99%can be achieved within 60minutes;At the same time,the degradation of phenol is 20%more efficient than pure TiO₂.（2）Prepare two-dimensional flake g-C₃N₄ by high-temperature calcination method,and synthesize g-C₃N₄/TiO₂ composite photocatalyst by ultrasonic dispersion method.Utilizing the formed heterojunction structure not only improves the response ability of the catalyst to visible light,but also promotes the separation of electrons and holes.UV-Vis DRS showed that the absorption of visible light by g-C₃N₄/TiO₂ composite material was enhanced,and its band gap width was reduced from 3.07e V to 2.73e V,and when the g-C₃N₄ content is 20%,under simulated sunlight radiation,the catalyst has the best photodegradation performance for Rh B and MO.Cyclic degradation experiments show that g-C₃N₄/TiO₂ has good stability and shows its application value in the field of purifying dye wastewater.