Systhesis And Visible Photocatalytic Properties Of Composite Based On Titanium Dioxide

Environmental pollution and energy crisis have become the most important and difficult problem in recent years. And it is becoming an overwhelming concern all over the world. Photocatalysis technology is regarded as a reasonable method due to easy and simple to handle, low energy consumption and no secondary pollution. Therefore, many specialists devote themselves to research more suitable, more novelty, more efficient catalytic agent. Titanium dioxide（TiO₂） is the research hotspot among most reseachers and is one of the most widely used nanomaterials in the energy and environment field owing to the high specific surface area, nontoxicity and the high chemical stability.Such as dye sensitized solar cell, supercapacitor, lithium ion battery, photocatalysis, and so on. However, TiO₂ as a widely used wide band-gap（rutile³.0, anatase³.2 eV） semiconductor, always requires ultraviolet（UV） light to excite the generation of electron hole pairs to ensure photocatalysis. Nevertheless, UV light takes up only a small fraction（below 10 %） of the sun’s energy compared to visible light（about 44 %）. TiO₂ nanomaterial has limited sunlight utilization. So it is more meaningful to prepare the visible-light response nanocomposite based on TiO₂ by doping vario-property. In here, we use an electrospinning method combined with a hydrothermal approach to synthesize the TiO₂ nanocomposite. And these TiO₂ based heterostructures exhibit great potential for decontamination of organic pollutants in waste water under visible light and good recyclability. The main contents are as follows:（1） CdS/TiO₂ composite have been successful prepared for the photocatalysis toward organic dyes under visible irradiation. The one dimensional（1D） TiO₂ porous nanofibers（50¹00） nm in diameter and several micrometers in length were synthesized by electrospinning and then CdS nanoparticles（50¹00 nm in size） successfully grown onto TiO₂ fibers to form the heterostructure. These CdS/TiO₂ heteronanofibers were adopted as photocatalyst and the photocatalsis processes were analyzed in detail, showing the enhanced visible photodecomposition and good recycle ability. CdS component may enhance the degradation rate under visible light, but the total degradation efficiency also is affected by the adsorption capacity of catalyst toward the dyes. With the improved visible light degradation performance, these CdS/TiO₂ heteronanofibers would be expected to be used in water purification.（2） TiO₂/porous carbon nanofibers（TiO₂/PCNFs） were prepared for visible photocatalysis for dye degradation. PCNFs were synthesized via an electrospinning technique, exhibiting a highly porous structure and large surface area. After hydrothermal treatment, TiO₂ nanorods were deposited onto the PCNFs to obtain a TiO₂/PCNFs heterostructure. By adjusting the amount of Ti source material, the amount of TiO₂ nanorods could be easily controlled. Congo red（CR）, methylene blue（MB）, methyl orange（MO） and eosin red（ER） were adopted as the model dye molecules, and the adsorption and visible photocatalysis studies were carried out in depth. All of the TiO₂/PCNFs exhibit an enhanced visible photocatalytic efficiency and good recyclability due to the large surface, improved visible light absorption and high separation efficiency of the photogenerated electron/hole. In particular, TiO₂/PCNFs-4 possesses the ability to efficiently decolor MB solution even with a high concentration（120 mg /L, 70 min）, ascribed to the high adsorption capacity derived from the strong electrostatic interaction and structure match between TiO₂/PCNFs-4 and MB.（3） A branch-like α-Fe2O3/TiO₂ composite has been synthesized controllably through an electrospinning method combined with a hydrothermal approach. The backbone of the heterostructure is composed of porous TiO₂ nanofiber（70 nm in diameter） network with plenty of α-Fe2O3 nanorods（100²00 nm in length） deposited on them. The novel branch-like nanocomposites have an abundantly porous structure as well as large surface areas（up to 42.8 m2 /g）. In addition, their visible light photodegradation behaviour towards organic dyes was investigated. These α-Fe2O3/TiO₂ heterostructures exhibit great potential for decontamination of organic pollutants in waste water under visible light.