Effects of N Doping on the Microstructures and Optical Properties of TiO2

TiO2 nanopowders with different nitrogen (N) dopant concentrations were first synthesized by sol-gel method. XRD, TEM, HRTEM, XPS, UV-vis DRS were used to characterize the effects of N doping on the microstructures and optical properties of TiO2. The results indicated that the prepared TiO2 only contained anatase phase with a slight distortion, and the N doping improved the dispersity of TiO2. The N doping leaded to more defects in TiO2, capturing the charge carriers and inhibiting the combination of electrons and holes. Also, the N-doped TiO2 was composed of Ti, O and N. Further, N was doped into the TiO2 lattice by substituting for O, forming the oxidized nitrogen in the form of Ti–N–O or Ti–O–N bond, and Ti was present in the form of Ti4+ in TiO2. Finally, the absorbance of N-doped TiO2 was obviously improved in both UV and visible light region. Optical absorption edges of N-doped TiO2 samples showed obvious red shift, which expanded spectral absorption range of TiO2 and improved the utilization efficiency of visible light. It is concluded that N element was successfully doped into TiO2 crystal lattice, and the N dopant concentration of 3.0% was designed to modify TiO2.