N-doped mesoporous TiO2 nanoparticles synthesized by using biological renewable nanocrystalline cellulose as template for the degradation of pollutants under visible and sun light

Yellow-colored N-doped mesoporous TiO 2 photocatalyst (TiO 2 -NT) with visible-light response was prepared by a hydrolysis–precipitation method at different urea contents with the use of nanocrystalline cellulose (NCC) as template. The photocatalytic activity was investigated through the degradation of phenol, nitrobenzene, and methyl orange (MO) under artificial visible and sun light irradiation. X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse spectroscopy (DRS), X-ray diffraction (XRD), thermogravimetry–differential thermal analysis (TG/DSC), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and N 2 adsorption–desorption isotherms were used for catalyst characterization. The results showed that NCC-templated TiO 2 with a suitable N-doping content (TiO 2 -NT) exhibited higher activity under visible and sun light irradiation than N-doped TiO 2 synthesized without NCC template (TiO 2 -N). Affected by the hydroxyl groups of NCC macromolecule and the Ti precursor, the growth and aggregation of TiO 2 precursor before calcination were inhibited. The NCC template led to high dispersion, small grain size, and high specific surface area of TiO 2 -NT. Nitrogen doping was proposed to adjust band gap and electrical properties of TiO 2 by establishing acceptor defect. N-doped TiO 2 with the intrinsic donor defect of oxygen vacancy and the nitrogen-to-oxygen acceptor defect could be excited by visible irradiation for efficient pollutant degradation.