Synthesis and photocatalytic activity of nanocrystalline TiO2 co-doped with nitrogen and cobalt(II)

Nitrogen-modified cobalt-doped TiO2 materials were successfully prepared via a modified sol–gel method. The structure and properties of the catalysts were characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM, ultraviolet–visible light diffuse reflectance spectra (UV–Vis DRS), N2 adsorption–desorption isotherms, and energy-dispersive X-ray spectroscopy. The XRD patterns of the pure and co-doped TiO2 samples indicate that the predominant phase was anatase. The average grain size obtained from TEM was approximately 10 nm. The Brunauer–Emmett–Teller analysis results indicate that the specific surface area was 77.7 m2 g−1. The UV–Vis DRS results for the co-doped sample reveal an absorption edge that had been red-shifted to 500 nm. The photocatalytic activities of the samples were evaluated through photodegradation of papermaking wastewater under UV and visible light irradiation. Compared with the cobalt-doped TiO2 sample and Degussa P25, the 3 mol% N-doped mesoporous N/Co-TiO2 photocatalyst exhibited the highest photocatalytic activity, which can be ascribed to the synergistic effect of the N and Co co-doping.