Structural Design And Photocatalytic Performances Of Titania-Based Photocatalysts

Titanium dioxide（TiO₂）has the advantages of stable physicochemical properties,good light-response ability and high refractive index.It is widely used in luminescence,photocatalysis and so on,which is regarded as one of the most promising semiconductor photocatalysts.However,the application performance of TiO₂ is greatly affected by its shortcomings such as easy phase transformation,easy aggregation,narrow light response range and lack of selectivity.In this thesis,TiO₂-based photocatalysts with excellent performance were prepared though morphological design,energy band structure regulation and other strategies.The structure-activity relationship of the catalysts was studied.The stability of the catalysts and their ability to resist the interference of environmental factors were evaluated.The photodegradation pathway and the toxicity of degradation intermediates were studied.The reasons for improving photocatalytic performance and the mechanism of photodegradation were revealed.The main research results are as follows:1.A series of three-dimensional（3D）Eu³⁺doped yolk shell TiO₂ bifunctional catalysts with different geometric sizes,crystal phases and crystallinity were fabricated by using silica as a sacrificial template using the sol-gel method and calcination etching process.The relationship between luminescence intensity,photodegradation performance and morphology was studied.It was proved that yolk shell photocatalysts can effectively promote carrier separation.The effects of the size,crystal phase composition and crystallinity of the yolk-shell photocatalyst on the luminescence and photocatalytic performance of the bifunctional catalyst were systematically studied.Under the excitation of 463 nm,the samples exhibit Eu³⁺characteristic red-light emission.The coordination environment of Eu³⁺was determined by Judd-Ofelt theory and the mechanism of Eu³⁺improving the photocatalytic performance was explored.The process of photodegradation of tetracycline（TC）was fitted by pseudo-first-order and second-order kinetics at the same time,and the influencing factors were revealed.The photodegradation pathway was speculated and the photodegradation mechanism of yolk-shell TiO₂ catalyst was revealed.This study provides the experimental basis for the rational design of yolk-shell photocatalyst,and enriches the structural design strategy of high-performance photocatalyst.2.One-dimensional（1D）inorganic-framework molecularly-imprinted TiO₂/Si O₂hybrid fiber was prepared by electrospinning and calcination process.A series of inorganic molecular-imprinted photocatalysts with different imprinting concentrations were prepared by changing the amount of template molecules added.By studying the adsorption and photocatalytic properties of the catalysts,the amount of template molecules added was optimized.The adsorption properties of the molecularly imprinted photocatalyst were discussed in detail.The adsorption mode of the catalyst for the template molecule rhodamine B（Rh B）was investigated.It was proved that the adsorption capacity and selectivity of the catalyst for Rh B were improved by the modification of the molecular imprinting modification.The one-dimensional inorganic-framework molecular-imprinted TiO₂/Si O₂ hybrid fiber catalyst prepared in this thesis has excellent stability and anti-interference ability of environmental factors.It can completely degrade Rh B within 15 min and possess excellent selective degradation performance for Rh B.The selective adsorption and photodegradation mechanism of one-dimensional inorganic-framework molecularly imprinted TiO₂/Si O₂ fiber was revealed.This study provides a new strategy for the construction of efficient inorganic framework molecularly imprinted photocatalysts.3.The magnetic inorganic-framework molecularly imprinted 3D/1D composite structure Fe₃O₄@TiO₂-TiO₂/Si O₂ photocatalyst was prepared by electrospinning method.The addition of template molecule TC and the addition of three-dimensional molecular imprinted structure in one-dimensional fibers were optimized.The adsorption method of the catalyst for TC was determined by the adsorption performance test.It was proved that the catalyst had affinity and selectivity for the adsorption of the template molecules.The photodegradation performances of the catalysts were studied,and the influence of various factors on the photodegradation performance was discussed in detail.The catalyst can completely remove TC within 20 min,and possesses excellent stability,selectivity,resistance to environmental factors and recyclability.The interaction between the catalyst and TC was confirmed by series characterization analysis and IGMH theoretical calculation.The degradation pathway was speculated and the toxicity of the degradation intermediates was analyzed.The photocatalytic degradation mechanism of the 3D/1D composite structure catalyst was revealed,which provided a new idea for the construction of efficient photocatalyst and a new strategy for the efficient and selective treatment of pollutants.