Nitrogen doped TiO2 nanotube arrays with high photoelectrochemical activity for photocatalytic applications
Graphical abstract
Photocurrent spectra of as-prepared TiO2 nanotube arrays and N-doped TiO2 nanotube arrays. A pure TiO2 nanotube arrays without annealing, b pure TiO2 nanotube arrays annealed at 500 ̊C; N-doped TiO2 nanotube arrays annealed at different temperatures, c 300 ̊C, d 400 ̊C, e 500 ̊C, f 600 ̊C, g 700 ̊C. The inset shows the photocurrent versus annealing temperature of N-doped TiO2 nanotube arrays.
Introduction
Nanostructured materials, especially the highly ordered nanotube materials, have attracted a great deal of attention in various fields. In recent decades, the preparation of nanomaterials has diversified with the development of science and technology. Advances in the nanoscale technology [1] facilitated the fabrication of highly ordered and multidimensional structured materials. Many efforts have focused on new synthesis methods and photoelectrochemical properties of the tubular structure, large specific surface area, oriented charge transfer channel and the other distinct properties. TiO2 nanotube arrays as nanostructure semiconductor compound have attracted increasing research interests in photocatalysis [2], [3], [4], [5], dye sensitized solar cells [6], [7], gas sensors [8], [9], biomedical applications [10] and so on. Particularly, TNAs are expected to exhibit better photocatalytic properties compared with nanoparticles or other forms of titanium dioxide [11], due to their high specific surface area, short diffusion path and high activity in the band-edge positions, which make it more suitable to be used as catalyst [12].
Consequently, the synthesis or modification of TiO2 nanotube arrays have been widely studied [13], [14], and considerable efforts of fabrication TiO2 nanotubes such as hydrothermal treatment [15], template-deposition [16], sonoelectrochemical method [17] and anodic oxidation [18], [19] have been developed. Gong and co-workers [20] pioneered the synthesis of vertically ordered TiO2 nanotube arrays up to 500 nm in length by a potentiostatic electrochemical anodization of titanium in hydrofluoric acid aqueous electrolyte. The experimental process is very convenient without any complex apparatus. Subsequently, various organic electrolytes including dimethyl sulfoxide [21], formamide [22] and ethylene glycol [23] have been adopted to fabricate TiO2 nanotube arrays with greatly extended length.
Though TNAs as photocatalysts were firstly used in environmental applications [24], many challenges still remain such as the TNAs could not absorb visible light (λ > 387 nm) of the solar spectrum efficiently because of their large band gap (3.2 eV) as well as the recombination of photogenerated electrons and holes. In order to overcome these disadvantages, considerable efforts have been made to modify TNAs in order to reduce the band gap. In the present case, many transition metal ions [25], [26] and nonmetal ions [27], [28], [29], [30] have been studied to increase the visible light absorption or suppress the recombination of photogenerated electron–holes. Asahi et al. [31] investigated a visible-light photocatalysis in nitrogen-doped titanium oxides by sputtering the TiO2 target in a N2/Ar gas mixture. Tokudome and co-workers [32] reported nitrogen-doped TiO2 nanotubes by a wet process. In this paper, nitrogen doped TiO2 nanotube arrays (N-TNAs) were fabricated by immersing TNAs in ammonia aqueous solution following with annealing in air atmosphere. Effects of annealing temperature on the photocatalytic performance of N-TNAs were investigated.
Section snippets
Preparation of nitrogen doped TiO2 nanotube arrays
Highly ordered TiO2 nanotube arrays were fabricated by anodization method. Titanium foil was anodized in ethylene glycol electrolytes containing 0.3 M ammonium fluoride and 2 vol% water with potential of 60 V for 6 h. The as-prepared TNAs samples were immersed in 1 M NH3·H2O solution for 10 h and then annealed in a tube furnace for 2 h at different temperatures with heating and cooling rates of 2 ̊C/min.
Characterization of N-TNAs
The surface morphologies of samples were observed using the field-emission scanning electron
The morphology of TNAs and N-TNAs
SEM morphologies of typical TNAs are shown in Fig. 1. The TNAs are well-aligned with average diameter of 140 nm, wall thickness of 10 nm, and length of 30 μm. The morphologies of N-TNAs are shown in Fig. 2. N-TNAs annealed at 500 ̊C are shown in Fig. 3. Both undoped and the N-doped TiO2 nanotube arrays annealed at 500 ̊C show similar morphologies with the as-fabricated TNAs. These results indicate no significant effect of annealing on surface morphology and microstructure of the TNAs. However, the
Conclusions
In this study, TiO2 nanotube arrays were successfully prepared by anodization. N-doped TiO2 nanotube arrays were then synthesized by immersing the TNAs into the ammonia aqueous solution. The XPS characterization results showed that the N-TNAs were mainly achieved through substitutional doping and interstitial doping. And the morphology was not changed after annealing and doping process. Photoelectrochemical experiment showed that photocurrent and photocatalytic activity of N-TNAs strongly
Acknowledgements
This work was financially supported by the National Natural Science Foundation of China (Nos. 91023030, 51272062, 51128201 and 51202052), Natural Science Foundation of Anhui Province (No. 1308085QE74), the Specialized Research Fund for the Doctoral Program of Higher Education (No. 20100111110012) and the International Scientific and Technological Cooperation Project of Anhui Province (No. 10080703017).
References (42)
- et al.
Effects of structure of anodic TiO2 nanotube arrays on photocatalytic activity for the degradation of 2,3-dichlorophenol in aqueous solution
Journal of Hazardous Materials
(2009) - et al.
Highly sensitive and pulse-like response toward ethanol of Nb doped TiO2 nanorods based gas sensors
Sensors and Actuators B
(2012) - et al.
The effect of TiO2 nanotubes in the enhancement of blood clotting for the control of hemorrhage
Biomaterials
(2007) - et al.
Synthesis of anatase TiO2 nanoparticles with high temperature stability and photocatalytic activity
Solid State Science
(2008) - et al.
Synthesis, characterization of TiO2 nanotubes-supported MS (TiO2NTS@MS, M = Cd, Zn) and their photocatalytic activity
Journal of Solid State Chemistry
(2007) - et al.
Electropolishing for the formation of anodic nanotubular TiO2 with uniform length and density
Applied Surface Science
(2011) - et al.
Fabrication of TiO2 nanotubes by using electrodeposited ZnO nanorod template and their application to hybrid solar cells
Electrochimica Acta
(2008) - et al.
A novel method for the synthesis of titania nanotubes using sonoelectrochemical method and its application for photoelectrochemical splitting of water
Journal of Catalysis
(2007) - et al.
Effect of copper ions on the formation of hydrogen peroxide from photocatalytic titanium dioxide particles
Journal of Catalysis
(2003) - et al.
Biomolecule-controlled hydrothermal synthesis of C–N–S-tridoped TiO2 nanocrystalline photocatalysts for NO removal under simulated solar light irradiation
Journal of Hazardous Materials
(2009)
Effect of surface defects on biosensing properties of TiO2 nanotube arrays
Sensors and Actuators B
Nitrogen-doped TiO2 nanotube array films with enhanced photocatalytic activity under various light sources
Journal of Hazardous Materials
Self-organized TiO2 nanotube layers as highly efficient photocatalysts
Small
Enhanced photocleavage of water using titania nanotube arrays
Nano Letters
Daylight photocatalysis by carbon-modified titanium dioxide
Angewandte Chemie International Edition
Palladium oxide nanoparticles on nitrogen-doped titanium oxide: accelerated photocatalytic disinfection and post-illumination catalytic memory
Advanced Materials
Use of highly-ordered TiO2 nanotube arrays in dye-sensitized solar cells
Nano Letters
Dye-sensitized solar cells based on oriented TiO2 nanotube arrays: transport, trapping, and transfer of electrons
Journal of the American Chemical Society
Extreme changes in the electrical resistance of titania nanotubes with hydrogen exposure
Advanced Materials
Template-assisted fabrication of dense, aligned arrays of titania nanotubes with well-controlled dimensions on substrates
Advanced Materials
Determination of a morphological phase diagram of titania/titanate nanostructures from alkaline hydrothermal treatment of Degussa P25
Chemistry of Materials
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