N-loaded TiO2 for photocatalytic degradation of methyl orange under visible light irradiation
Nitrogen-loaded TiO2 (N-loaded TiO2), a visible-light driven catalyst, was successfully synthesized by the modified sol-gel method. Physical characterizations of the as-prepared catalysts have been performed by using X-ray diffraction (XRD), Diffuse reflectance UV−vis spectroscopy (DR UV−vis), Raman spectroscopy and BET specific surface area in order to obtain structure-activity relationship. Results from Raman spectroscopy clearly suggested that N atoms were incorporated into the TiO2 crystal lattice as evidenced by the vibrational peak of Ti−N in TiO2-xNx. DR UV−vis results also suggested that the nitrogen dopant might be responsible for narrowing the TiO2 band gap energy, thus resulting in a shift towards the visible light region. Photocatalytic activity of N-loaded TiO2 evaluated through the degradation of methyl orange (MO) under visible light irradiation (λ > 400 nm) indicated that all N-loaded photocatalysts exhibited significantly higher activities than the unloaded TiO2 and Degussa P25 TiO2. According to the results from DR UV-vis, XRD and BET studies, the enhanced photoactivity observed from N-loaded samples might be due to a decrease in TiO2 band gap energy and/or changes in chemical and physical properties of the materials upon loading with nitrogen.