TiO₂ nanoparticles doped with different content of nitrogen were prepared by sol-gel method, and preliminarily characterized by means of XRD, TEM and UV-vis spectra. The concentration of nitrogen of N/TiO₂ was detected using XPS and elemental analyzer method (EA). It was confirmed by XPS that oxygen sites were substituted by nitrogen atoms and Ti^3＋ species was formed on the surface of the nitrogen-doped titania; UV-visible reflectance spectra measured the band gap (E_g) of nitrogen-doped titania in different content, which indicated that an N-induced midgap level was formed from above the valence band (O 2p). The E_g of N/TiO₂ could be estimated to be 2.50 eV when the molar ratio of N to Ti was 0.0880, which was narrowest. The photocatalytic degradation of sulforhodamine-B (SRB) and 4-chlorophenol (4-CP) in aqueous solution was used as probe reactions to evaluate their photocatalytic activity with different doped content. It indicated that the N/TiO₂ powder with molar ratio n_N/n_Ti＝0.0880 exhibited highly catalytic activity for degradation of SRB under visible light irradiation. The formed oxidation species, total organic carbon (TOC), chemical oxygen demand (COD_Cr) and infrared spectrophotometry (IR) assays showed that the mechanism of photocatalytic degradation involved the excitation of electrons from the isolated N 2p orbitals to the Ti 3d orbitals, generating •OH for degradation of organic compounds.

Key words: TiO₂, nitrogen-doped, photocatalysis, degradation