Preparation and properties of visible light responding N-doped TiO₂ nanopowder by hydrothermal synthesis

By using technical grade TiOsO₄ as the precursor and urea as the precipitating agent, N-doped TiO₂ nanopowders were prepared by hydrothermal homogeneous precipitation and heat treatment. The properties of the prepared powders were characterized by XRD, XPS, BET, UV-Vis absorbance spectra, FTIR, and BET methods. By using an electronic energy-saving lamp as the light source, taking methylene blue as the model pollutant, their photo catalytic activities under visible-light irradiation were also investigated. The result showed that the products after 900℃ heat treatment were all anatase. When the temperature came to 1000℃, almost all of them were converted into rutile. Taking urea as the nitrogen source, XPS analyses of particles prepared by hydrothermal powders after heat treatment indicated that the Nls peak was close to 399 eV, Furthermore, N replacing a small amount of lattice oxygen to form TiO_2-xN_y(y ≥ x) was further demonstrated by FTIR. UV-Vis absorbance spectra showed that adding the nitrogen source during heat treatment was necessary to the red-shifted in the absorption band-edge and the binding ratio of photo-generated electrons. The particle size calculated by XRD accorded with the result analyzed by TEM, All results show that nitrogen-doped TiO₂ after heat treatment had a higher photo catalytic activity in visible light.