Study On Preparation Of Nitrogen-doped TiO₂and The Photocatalytic Enhancement By Mesoporous Carbon Support

Nitrogen-doped TiO2photocatalyst with a high photocatalytic activity was prepared with employing triethylamine as nitrogen source, through a low temperature hydrothermal method without further calcinations. Mesoporous carbons (MC) with different pore sizes, synthesized by using colloid silica as template, were employed as supports to prepare N-TiO2/MC nanocomposites through a hydrothermal process. The morphology, crystal structure, physical and chemical properties were characterized by the aid of BET, SEM, TEM, XRD, EL and TG. Light response and photocatalytic activity of the samples were evaluated by UV-Vis absorbance spectra and photocatalytic degradation of methyl orange (MO) in aqueous solutions under different light irradiations. The main results are as follows:1) N-TiO2synthesized under suitable conditions (pH=3,170℃) exhibited the best photocatalytic activity in both UV and visible light irradiations, which is attributed to its remarkable anatase phase of TiO2, the smallest particle size, the most absorption in UV-Vis spectra range as well as the highest nitrogen concentration (0.89at.%).2) Mesoporous carbons prepared through nanosized SiO2templates with the sizes of7nm and12nm, were employed as supports for N-TiO2loading. Compared with12nm N-TiO2/MC,7nm N-TiO2/MC exhibited higher surface area, larger pore volume, smaller and more uniform N-TiO2particle size, providing higher photocatalytic activity for degradation of methyl orange under visible-light irradiation.3) In the composites with different N-TiO2/MC weight ratios, the actual amount of N-TiO2through TG analysis was proved to be consistent with the theoretical one. The MO removal rate of all composites reached50-60%in dark. N-TiO2content of50wt.%was an optimal value in the composite for photodegradation under visible-light irradiation with its removal rate reaching77.5%in75min, which largely outperformed that of unloaded N-TiO2. The N-TiO2/MC composite loaded by70wt.%exhibited the highest photoactivity under UV irradiation.4) The degradation rate of N-TiO2/MC composite decreased only2.1%after three cycles under visible-light irradiation, which demonstrated better recyclability compared with that of unloaded N-TiO2.