Photocatalytic Degradation of 4-Nitrophenol on Well Characterized Sol-Gel Molybdenum Doped Titania Semiconductors

Mesoporous TiO2-Mo materials with different Mo contents (0-5.0 wt%) were synthesized by the sol-gel method. In samples annealed at 500 degrees C, specific surface areas ranging from 150 to 86 m(2)/g were obtained. X-ray diffraction spectra denoted that the titania anatase phase (similar to 28 nm) was significantly strengthened by the presence of Mo. The UV-vis diffuse reflectance spectra showed that the band gap was shifted to lower energy levels in the samples with higher Mo contents. Fourier transform infrared analysis evidenced that the hydroxylated samples persisted after annealing at 500 degrees C. X-ray photoelectron spectroscopy analyses showed the presence of Mo4+ and Mo6+ species, where Mo6+ can be transformed from this state to a lower oxidation state during the annealing treatments. The study of the photocatalytic degradation of 4-nitrophenol (4-NP) showed that the activity can be related to the c cell parameter of the anatase phase in the Mo-doped semiconductors. Total mineralization of 4-NP up to 98% (TOC) was obtained in the sample (1.0 wt% Mo) with the highest photoactivity.