This paper introduces a novel method for characterizing the oxygen vacancy associates in hydrogenationmodified TiO 2 by using a positron annihilation lifetime spectroscopy (PALS). It was found that a huge number of small neutral Ti 3+ −oxygen vacancy associates, some larger size vacancy clusters, and a few voids of vacancy associates were introduced into hydrogenated TiO 2 . The defects blurred the atomic lattice high-resolution transmission electron microscopy (HRTEM) images and brought about the emergence of new Raman vibration. X-ray photoelectron spectroscopy (XPS) measurement indicated that the concentration of oxygen vacancies was 3% in the TiO 2 lattice. The photoluminescence (PL) spectroscopy, photocurrent, and degradation of methylene blue indicated that the oxygen vacancy associates introduced by hydrogenation retarded the charge recombination and therefore improved the photocatalytic activity remarkably.

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Being expected as one of the most promising solutions in water and air purification as photocatalyst, TiO 2 is attracting intensive and extensive research interests globally despite its wide band gap (~3.2 eV for anatase structure) which limits it only to be activated under UV irradiation. In pursuit of extending the active region of TiO 2 toward visible light, considerable attention was devoted to develop TiO 2 -based photocatalyst. We report herein, for the first time, novel "bud-on-branch" Bi 2 WO 6 -TiO 2 nanofibers fabricated via a facile and largescale electrospinning technique from a biphased precursor. Formed by surface-decorating continuous TiO 2 nanofibers (mixed anatase-rutile system with an average diameter of about 100 nm) with~13 nm well-crystallized Bi 2 WO 6 nanoparticles, the as-synthesized Bi 2 WO 6 -TiO 2 nanofibers achieved an evidently increased specific surface area. Furthermore, corresponding photocatalytic experiments revealed that the optimal photodegradation rate from our designed heterostructure was as high as three times to that of pure TiO 2 nanofibers; this increase in optimal photodegradation rate is attributed to the relatively well-matched energy band between TiO 2 and Bi 2 WO 6 and hence an excellent separation efficiency of photogenerated electron-hole pairs in both ultraviolet and visible light regions, suggesting that the designed heterostructures can give better rise to practise photocatalysis under natural light.

This article introduces a novel and valid process for preparing a high concentration substitutional N‐doped TiO2 photocatalytic film, i.e. firstly the titanium substrate was plasma nitrided and then the N‐doped TiO2 was synthesized on the surface of nitrided titanium by using micro‐arc oxidation. Compared with the traditional thermal annealing, the present process provides a possibility to increase the nitrogen doping concentration up to 3.21 at.% and x to 0.11 in TiO2–xNx, which exhibits a significant red‐shift in the band‐gap transition, narrow band gap to 2.6 eV, higher photo‐generated charge carrier density and improved photocatalytic property.

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