Photocatalytic Properties Of TiO₂-based Nanomaterials Prepared Via Electrospinning

With the development of science and technology, environment pollution and energy crisis have become the two big problems which the human’s survival and development have to face. The semiconductor photocatalytic technology is one of the important ways to solve these two big problems, and also is the people’s research hotspot at present. As a kind of the most commonly used semiconductor photocatalyst, TiO2has many advantages such as non-toxic, chemical stability, excellent acid-proof alkaline, high photocatalytic efficiency and stable photocatalytic properties, etc. However, the photocatalytic TiO2can only absorb ultraviolet light to the catalytic degradation of organic pollutants, so it will have great realistic significance and research value to improve the visible light photocatalytic activity of TiO2, which can efficiently degrade organic pollutants under the irradiation of sunlight. Many researches report that TiO2coupling with a narrow band gap semiconductor or being modified by silver can extend the visible light absorption of the catalyst and promote the separation of the photogenerated electrons and holes, which will improve the visible light photocatalytic efficiency of TiO2. But there are some shortage in the researches about these two methods. In this paper, we focus on improving the visible light photocatalytic efficiency of TiO2using these two methods, we study the enfluencement of the experiment parameters to the visible light photocatalytic efficiency of TiO2-based nanomaterials. Moreover, we propose the photocatalytic mechanism of the TiO2-based nanomaterials. The TiO2-based nanomaterials are all prepared by one-step electrospinning method and the main results of the present work are as follows:(1) TiO2/V2O5nanoheterostructures are prepared by one-step electrospinning method and the visible light photocatalytic activity is studied. V2O5can extend the absorption spectrum of TiO2and promote the separation of the photogenerated electrons and holes, rhis can improve the visible light photocatalytic efficiency of the catalysts. The experiment results show that V2O5/TiO2nanoheterostructures have higher visible light photocatalytic activity than that of pure TiO2nanofibers. In addition, the nanoheterostructures show excellent photocatalytic stability. We studied the influence of annealing temperature on the morphology, structure and visible light photocatalytic efficiency of the TiO2/V2O5nanoheterostructures. The experiment results show that the visible light photocatalytic activity decreases with the increase of annealing temperature, and the optimal annealing temperature is400℃. This may be due to the grain size of TiO2and V2O5increases with the increase of annealing temperature, where the heterostructure area in V2O5/TiO2nanoheterostructures decreases, so the photocatalytic activity decreases. At the same time, the influence of V/Ti molar ratio on the morphology, structure and visible light catalytic efficiency of TiO2/V2O5nanoheterostructures is studied. The results indicate that the appropriate amount of V2O5can improve the photocatalytic activity, and the optimum V/Ti molar ratio of1:1. This may be ascribe to the influence of V/Ti molar ratio on the morphology and the heterostructure area in V2O5/TiO2nanoheterostructures.(2) The TiO2is modified with silver to improve the visible light photocatalytic activity. The Ag/TiO2nanomaterials are prepared by one-step electrospinning method and the visible light photocatalytic efficiency of the Ag/TiO2nanomaterials is studied. The experiment results show that the visible light photocatalytic efficiency of Ag/TiO2nanomaterials is higher than the pure TiO2nanofibers. This can be ascribed to the electronic excitation of Ag nanoparticles under visible light and the transfer of the electrons to TiO2conduction band. The influence of annealing temperature on the morphology, structure and visible light photocatalytic efficiency of Ag/TiO2nanomaterials is investigated, and the results indicate that the optimal annealing temperature is400℃, this may be due to the transformation of the anatase TiO2to the rutile phase with the increase of annealing temperature. Furthermore, the influence of Ag/Ti molar ratio on the morphology, structure and visible light photocatalytic efficiency of Ag/TiO2nanomaterialss is studied, and the optimum Ag/Ti molar ratio is5%. This may be ascribe to the appropriate amount of Ag can improve photocatalytic activity. However, superfluous Ag nanoparticles would hinder the contact between TiO2and organic molecules, in which the electrons cannot easily combine with oxygen, so the photocatalytic activity would decrease.