We have obtained nitrogen-doped titania microspheres with the general formula of TiN1-xOx from the annealing of TiO2 microspheres in the presence of ammonia (NH3). The parent TiO2 microspheres were prepared using a sol-gel method, whose diameters in the range of 370 to 420 nm. Nitrogen contents in the TiN1-xOx samples were controlled by the annealing temperature and time. The TiN1-xOx microspheres were fully characterized by X-ray powder diffraction, elemental analysis, thermo gravimetric analysis, transmission electron microscope, scanning electron microscope, energy dispersive spectrometry, UV-visible absorption spectroscopy, and Raman spectroscopy. UV-visible absorption spectra of all the TiN1-xOx samples show broad absorption peaks in the visible-light region, indicating that the TiN1-xOx samples are photo-catalytically active under the visible light. The TiN1-xOx catalysts show enhanced activities toward the decomposition of methylene blue under visible-light irradiation presumably as a result of oxygen vacancy and formation of Ti3+ species created by the nitrogen doping. Their photo-electrochemical properties were also investigated by chronoamperometry measurements under an applied potential of 0.8 V (vs. Ag/AgCl) and a periodic irradiation of visible-light (=420 nm). Upon irradiation, the current density drastically increased due to photo-generated electrons. In addition, we estimated the photo-catalytic activities of the TiN1-xOx samples using a photo-luminescence emission spectroscopy, which is excited at 315 nm in a terephthalic acid solution. The hydroxyl radical (�OH) generated by the irradiation reacts immediately with terephthalic acid to form 2-hydroxyterephthalic acid, which emits a fluorescence signal at about 425 nm. In combination with a series of experiments, we will present the photo-catalytic activities of TiN1-xOx in terms of the nitrogen doping level.

Visible-light sensitive nitrogen-doped titania microspheres and their photocatalytic activities

248th National Meeting (2014)

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