Controlled Synthesis of Multi-morphological Nano-TiO2 and Preparation and Characterization of TiO2-based Composite Photocatalyst

Author:Li Wei

Supervisor:ding hao


Degree Year:2019





Titanium dioxide(TiO2)is a semiconductor compound with excellent optical and photochemical properties.It is an important way to improve the quantization efficiency of nano TiO2,expand the optical response of TiO2 to the visible light range and improve its photocatalytic efficiency by adjusting the structure and morphology of TiO2,combining nano TiO2 with other semiconductors to form heterostructures and depositing noble metals on the surface.At present,there are some problems in this technical field,such as less kind of TiO2 morphology,poor scale matching between the composite semiconductor and the lack of research on three-component heterojunction.In view of these problems,it is necessary to carry out controllable synthesis of multi-morphological nano TiO2 and prepare TiO2-based composite photocatalyst.In this paper titanium oxysulfate(TiOSO4)is used as the source of titanium.By using alcohol-thermal method,three kinds of morphologies of nano TiO2 were controllable prepared including hollow tubes.Also preparation in the similar particle size of nano TiO2-CdS heterojunction,hollow tube TiO2-CdS-Au and nanosheet TiO2-ZnO-Au composite photocatalyst technology was studied.The as-prepared TiO2 and its composite photocatalyst phase morphology,structure and photocatalytic degradation of pollutants,water decomposition hydrogen production and antibacterial performance were characterized and the compound of components and formation mechanism of the photocatalyst were studied.The influence on the synthesis of nano-TiO2 with different morphologies and the properties of the products were studied.By changing the proportion(molar ratio)of TiOSO4,ethanol and propylene triol in the reaction system and reaction time,the hollow tubular and round nano-sheet TiO2 products can be obtained respectively.Without the addition of propylene triol,TiO2 nanoparticles can be obtained.TiO2 in each morphology was composed of anatase and rutile,and mainly anatase.Each TiO2showed the performance of photocatalytic degradation of methyl orange under UV-light irradiation,among which the hollow tubular TiO2 had the highest photocatalytic activity.The hollow tubular structure of TiO2 has the characteristics of micropore-mesoporous,which is formed by the extrusion of a large number of nano-sheet materials.The inner diameter of the tube is about 500nm,the wall thickness is about200nm,and the thickness of nano-sheet is about 10nm.There are structural micropores in the nano-sheet.The structure and photocatalytic properties of CdS-TiO2 heterostructure composite photocatalyst were studied.In CdS-TiO2,CdS and TiO2 have similar scales,and the primary particles are all at the nanometer scale(22nm and 12nm respectively),which are uniformly combined through their interfaces.Under visible light irradiation(8h),the degradation rate of tetracycline hydrochloride by CdS-TiO2(50%of CdS)was 87.06%,and the catalytic effect of visible light was significantly stronger than that of pure TiO2(synthesized TiO2 and P25)and CdS.The preparation of ternary composite photocatalyst and its structure,properties and mechanism were studied by supporting CdS and Au nanoparticles on the surface of hollow tubular TiO2.Among them,the photocatalytic activity of TiO2-CdS/Au prepared in the order of first supporting CdS and then supporting Au was stronger than that of TiO2-Au/CdS prepared in the order of first supporting Au and then supporting CdS.Hydrogen production of TiO2-CdS/Au reached 14mmol/g after visible light irradiation for 4h.The mechanism for the improvement of the efficiency of TiO2-CdS/Au is that Au is in the outermost layer of the core-shell structure,so its electron capture and surface plasmon resonance effect are effectively exerted,and thus the electron-hole separation efficiency of CdS is improved.TiO2-Au/ZnO composite photocatalyst was prepared by supporting nano ZnO and nano Au on TiO2 nano-sheet.TiO2-Au/ZnO has good visible light catalytic performance and antibacterial ability,and the hydrogen production capacity under visible light irradiation for 4h is 1068μmol/g.The antibacterial effect of TiO2-Au/ZnO coating film on Escherichia coli was 98.2%.