The Visible Light Photocatalytic Properties Investigates Of The Modified Nano TiO₂ Quasi-microspheres

In recent years,much attention has been paid for heterogeneous photocatalysis owing to its potential application in many areas,especially the treatment of environmental pollutants.Among semiconductor photocatalysts,TiO₂ is most frequently employed because of its non-toxity,low cost,high activity and strong stability in aqueous media.However,TiO₂ has two main disadvantages: Firstly,low quantum yield and low photocatalytic activity.Secondly,large band gap energy(3.2ev) which is only active to ultraviolet light and thus waste energy source.To solve the application technique problems of low utilization efficiency of solar energy and photon quanta for TiO₂ catalyst,people have done some studies to improve the performance of TiO₂ by doping metal elements or Dye-sensitized. Doping metal could induce defects on the surface of TiO₂,change the crystal,affect the reuniting of electrons and holes or broaden the photon-excited wavelength, hence change the photocatalytic activity of TiO₂.and the dye is excitated by capturing light,the excited electrons are immited into the conduction band of TiO₂, thereby enhancing the light response,herefore,how to modify TiO₂ in order to increase its photocatalytic activity and extend its range of photo-response spectrum is the key to further utilize in photocatalysis.In this paper,on the foundation of summarizing the development of the modification of nano-scaled TiO₂ photocatalyst,the following aspects were mainly studied.1.In order to improve the photocatalytic activity,TiO₂ were modified by doping Fe ions and V ions using Hydrothermal method.The particles of the powder prepared in this experiment were round shape with good dispersity and small size. When calcined at 773 K,the TiO₂ in composite catalysts exesits as anatase structure and its grain fineness number was between 100 and 700 nanometers.The obtained samples were characterized in detail via XRD,SEM,FTIR methods.The photocatalytic activity of metal-modified TiO₂ was studied by degrading the Methylene blue extra solution(MB).Meanwhile,the photocatalytic activity of samples were investigated particularly.Doping mechanism was investigated to find the results that showed that ions doping can lead to lattice aberrance,thus reducing the recombination of electron-cavity pairs and increasing quantum yield photocatalytic activities.The optimum doping concentration was different according to different doping ions.2.Using the organic dye modified TiO₂ to promote the light absorption to expand to visible light spectrum,While ruthenium polypyridyl complexes still represent the most efficient sensitizers so far,metal-free organic chromophores are increasingly applied in photocatalytic application by virtue of their high molar extinction coefficient,easy preparation,low cost,as well as their rich structures. The rich structures lead to diverse photophysical,photochemical,and electrochemical properties,which stimulate the continuous exploration of new types of organic dye molecules for photocatalytic application.8 - hydroxyquinoline complexes are often used as a liquid crystal display materials,can absorb light of different wavelengths.The article have synthesized the 8-hydroxyquinoline-5-sulfonic acid iron(â…¢) complexes in accordance with the molar percentage of 8-hydroxyquinoline-5- sulfonic acid:FeCl₃ = 3:1,we obtained samples' characters in detail via TGA-DSC,XRD,FTIR,NMR,Raman,UV-visible light spectrum methods.Proved that the 8-hydroxyquinoline-5-sulfonic acid iron(â…¢) complex is a three-coordinate structure and there are absorbency in visible light area.By comparing the degradation methyl orange effects of the 8-hydroxyquinoline-5-sulfonic acid iron(â…¢) complex,pure TiO₂,and the compound 8-hydroxy quinoline-5-sulfonic acid iron(â…¢)-TiO₂ photocatalyst,found that the complex photocatalyst having significant results.The photon excited wavelength of TiO₂ photocatalyst is broaden and the weakness of being unable to utilizate visible light is solved in the studies on improving the performances of TiO₂ photocatalyst by doping metal elements and dye-sensitize method in this thesis.The preparation method and various performances of modified TiO₂ photocatalyst are obtained and the laws affecting the photocatalytic activity of TiO₂ are got through systematically experimental study and various data analysis.