Abstract
A series of W, N codoped TiO2nanotube arrays with different dopant contents were fabricated by anodizing in association with hydrothermal treatment. The samples were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and ultraviolet-visible light diffuse reflection spectroscopy. Moreover, the photocatalytic activity of W and N codoped TiO2nanotube arrays was evaluated by degradation of methylene blue under visible light irradiation. It was found that N in codoped TNAs exists in the forms of Ti-N-O, while W exists as W6+by substituting Ti in the lattice of TiO2. In the meantime, W and N codoping successfully extends the absorption of TNAs into the whole visible light region and results in remarkably enhanced photocatalytic activity under visible light irradiation. The mechanism of the enhanced photocatalytic activity could be attributed to (i) increasing number of hydroxyl groups on the surface of TNAs after the hydrothermal treatment, (ii) a strong W-N synergistic interaction leads to produce new states, narrow the band gap which decrease the recombination effectively, and then greatly increase the visible light absorption and photocatalytic activity; (iii) W ions with changing valences in all codoped samples which are considered to act as trapping sites, effectively decrease the recombination rate of electrons and holes, and improve the photocatalytic activity.
Highlights
Nowadays, photocatalysis has attracted lively interest due to its potential applications in environmental remediation and clean energy production
The results demonstrated that the W and N codoped TiO2 nanotube arrays exhibited a higher photocatalytic activity than the single N-doped sample under visible light irradiation
It can be seen that all the diffraction peaks of N-TiO2 and W-N-TiO2-X can be ascribed to anatase TiO2, which indicates that W and N codoping has no effect on the crystal structure and phase composition of TiO2 nanotube arrays (TNAs)
Summary
Photocatalysis has attracted lively interest due to its potential applications in environmental remediation and clean energy production. Yang et al prepared C- and V-doped TiO2 photocatalysts by a sol-gel method with high photocatalytic activity for the degradation of acetaldehyde both under visible light irradiation (>420 nm) and in the dark [14]. Liu et al prepared a series of Ti1−xMoxO2−yNy samples using sol-gel method and found that Mo + N codoping can increase the up-limit of dopant concentration and create more impurity bands in the band gap of TiO2 by first-principles band structure calculations [15]. It reveals that Mo + N codoped TiO2 material is a promising photocatalyst with high photocatalytic activity under visible light. The mechanism of visible light photocatalytic activity enhancement was discussed
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