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To extend the photo response of TiO2 further into the visible light region, TiO2 nanotube arrays codoped with vanadium and nitrogen were synthesized by anodization process, followed by impregnation and calcination process. X-ray photoelectron spectroscopy (XPS) revealed the existence of interstitial N and V (V4+ and V5+) in V, N codoped TiO2 catalysts, which was beneficial to narrow the bandgap and separating charges. Higher photocurrent density displayed by the V, N codoped TiO2 nanotube arrays showed that more photo-induced electrons were generated, therefore effectively improved the catalytic activity. V, N codoped samples were used for the photodegradation of methyl orange (MO) in aqueous solution in presence of H2O2. H2O2 is used to serve as an electron scavenger and a precursor for •OH radicals, thus significantly accelerating the photodegradation of MO under visible light irradiation. A synergistic effect between V, N codoped TiO2 catalyst and H2O2 contributed to the high degradation activity toward MO. [ABSTRACT FROM AUTHOR]

Highly ordered TiO2 nanotube arrays (TNAs) codoped with V and N were synthesized by electrochemical anodization in association with hydrothermal treatment. The samples were characterized by field emission scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The photocurrent and photocatalytic activity of codoped TiO2 nanotube arrays were investigated under visible light irradiation. Moreover, the production of hydroxyl radicals (⋅ OH) on the surface of visible light-irradiated samples is detected by a photoluminescence technique using terephthalic acid (TA) as a probe molecule. It was found that the V+N co-doped TiO2 nanotube arrays showed remarkably enhanced photocurrent and photocatalytic activity than undoped sample due to the V and N codoping. [ABSTRACT FROM AUTHOR]