Synthesis And Photocatalytic Activity Of Visible Light Response N-f-codoped TiO₂ Nanorod Arrays

With the increased awareness of environmental protection and the more acute problem of energy shortage, photocatalytic degradation of organic pollutants using semiconductor materials has become an important research topic in environmental protection. TiO₂ as a semiconductor material has attracted more concerns due to its nontoxicity, low cost, stability and reusable in environmental management and energy development. However, owing to its wide band gap of 3.2 eV for anatase phase, it can only be effective under ultraviolet (UV) light radiation, which is less than 5% of solar energy on the Earth's surface; the easy recombination of photoinduced electrons and holes result in a low quantum yield; the obvious drawbacks of TiO₂ powder photocatalyst are the agglomeration and reuse difficult. These seriously limit the practical application of TiO₂.Therefore, how to solve these problems to enhance the photocatalytic activity of TiO₂ becomes a research hotspot.Recently, several attempts have been made to extend the optical absorption to the visible light region and improve the photocatalytic activity. The feasible methods are as follows: the morphology or size control of TiO₂ nanostructure, noble metal deposition, coupled semiconductor, metal and nonmetal doping, etc. In this paper, simultaneous nitrogen and fluorine doped TiO₂ nanorod arrays on the glass substrates were achieved by liquid phase deposition method using ZnO nanorod arrays as templates with different calcination temperature. We investigated the effects of different preparation conditions on the ZnO nanorod arrays, and got the optimal parameters for preparing the ZnO nanorod arrays. Further, the N-F-codoped samples were characterized by TG,FT-IR,Raman,SEM,TEM,XPS,UV-vis and PL measurements. The results are as following :(1) The highly oriented N-F-codoped TiO₂ nanorod arrays grows perpendicular to the glass substrate and the TiO₂ nanorod with an average length of ⁷50 nm and diameter of 60¹00nm is composed of TiO₂ nanoparticles, and the size of TiO₂ nanoparticles is ¹0 nm.(2) With increasing calcination temperature, the phase transformation from amorphous to anatase occurred. And the N-F doping did not change the crystalline structure of TiO₂ and F doping promoted the increase of TiO₂ anatase.(3) N and F atoms entered the TiO₂ lattice and the N-F codoping exhibited significant improvement of visible light absorption.The photocatalytic activity of all samples were studied by the photodegradation of the organic pollutants of methylene blue aqueous solution under UV and visible light irradiation. The results exhibit that the N-F-codoped TiO₂ nanorod arrays samples calcined at 350 and 450°C for 2h demonstrated the best UV and visible light activity in all samples, respectively, which could be ascribed to the synergetic effect of the unique 1D nanorod arrays structure and some beneficial effects induced by the appropriate amount of N and F doping in TiO₂ nanorod arrays.