a b s t r a c tIn this paper, we report on the co-doping nitrogen and sulfur has been achieved in the TiO 2 nanotube array films by treatment with thiourea and calcination under vacuum at 500• C for 3 h. The samples were characterized by scanning electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible diffuse reflectance spectroscopy. XPS spectra revealed that N might coexist in the forms of N Ti O and N O Ti, S was incorporated into the lattice of TiO 2 through substituting oxygen atoms in the N + S co-doped TiO 2 nanotube array films. XRD patterns indicated that improved crystallinity was obtained for N + S co-doped TiO 2 nanotube arrays as compared to that of undoped TiO 2 nanotube arrays. In photoelectrochemical measurements, the photocurrent of N + S co-doped TiO 2 nanotube array films was greatly enhanced compared to that of undoped samples under visible light irradiation. And the photocatalytic activities of the samples were evaluated on the removal of methylene blue under visible light irradiation. The N + S co-doped TiO 2 nanotube array films showed a better photocatalytic activity than the undoped sample due to the N, S doping.

Mo,N-codoped TiO2nanotube arrays (TNAs) were fabricated by a two-step method consisting of electrochemical anodization and subsequent magnetron sputtering of Mo. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). The results showed that the Mo,N-codoped TiO2nanotube arrays exhibited higher visible light absorbance and remarkably enhanced photocurrent density and photocatalytic activity compared with single N-doped TiO2. The highly efficient photoelectrochemical and photocatalytic activity is associated with the codoping effect between Mo and N, which plays a key role in producing new states, narrowing the bandgap, and reducing the recombination thereby effectively improving the visible light absorption and photocatalytic activity of TNAs.

In this article, titanium oxide nanotube arrays (TiO2–NTAs) were fabricated by anodic oxidation in an ethylene glycol (EG) electrolyte solution containing 0.25 wt.% NH4F. By varying anodized time and annealed temperature, the obtained nanotube arrays behaved different photocatalytic (PC) activities and photocurrent properties. These samples were characterized by scanning electronic microscope (SEM), X-ray powder diffraction (XRD). It was indicated in SEM images that TiO2 nanotube manifests highly ordered structure which, however, has been completely destroyed when the temperature comes to 800°C. XRD manifested that TiO2 nanotubes with various kinds of length all possessed anatase crystallite when annealed at 500°C; meanwhile, with certain length, TiO2–NTAs annealed at series calcination temperature range of 300–600°C also presented anatase crystallite, which is gradually enhanced with the increment of temperature. At 700°C, mixed structure was observed which was made up of proportions of overwhelming anatase and toothful rutile. Methyl blue (MB) degradation and photocurrent measurement testified that TiO2–NTAs under 4 h oxidation and 3 h of 600°C calcination manifested the highest activity and photocurrent density.

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