Abstract: The nano-TiO₂ powders were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), diffuse reflectance spectra (DRS) and X-ray photoelectron spectroscope (XPS). The results show that nano-TiO₂ is transformed to rutile crystal after treating at 400℃ in N₂ atmosphere and the nano-TiO₂ particles obtained are uniform. Part N atoms are intruded into the TiO₂ crystals and substituted for some of O atoms, which produce oxygen defects. Those oxygen defects become the center of photo activity, which result in the increase of absorbed photons and the formation of broad band gap and make the absorption spectrum move to the visible light. The photocatalytic degradation of methylene blue shows that the visible light catalytic activity of nano-TiO₂ calcined in N₂ atmosphere is improved.

Key words: nano-TiO₂, heat treatment, atmosphere, visible-light catalytic