Preparation and properties characterization of visible-light-driven N-doped TiO ₂

Nitrogen doped visible-light-driven TiO ₂ photocatalyst was successfully synthesized by hydrothermal method. The structure, morphology and spectral properties of the photocatalyst were characterized by X-ray diffraction (XRD), scanning electron microscope(SEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectra (DRS). The XRD results showed that nitrogen doping inhibited the increase of crystallite size. XPS spectroscopy indicated nitrogen dopants were incorporated into TiO ₂ lattice. A shift of the absorption edge to the lower energy were observed using DRS spectroscopy. The photocatalytic activities of the samples were investigated by degradation of methyl orange(MO) under visible light irradiation. Using terephthalic acid as hydroxyl radicals(·OH) capturer, the quantity of ·OH formed in the photocatalytic reaction system were determined by fluorescence technique. It was found that all nitrogen doped samples showed higher photocatalytic activities than pure TiO ₂ sample. Which could be explained by the reason: the smaller crystallite size of nitrogen doped TiO ₂ sample improved the photogenerated charge separation and enhanced the efficiency of interfacial charge-transfer process; nitrogen doping narrowed the band gap of TiO ₂ and extended the absorption to visible light region. The results indicated that the photocatalytic performance of the photocatalyst increased with the molar ratio of N to Ti; the variation of the formation rate of ·OH was consistent with the photocatalytic activity, namely the greater formation rate of ·OH, the higher photocatalytic activity of sample.