Preparation And Photocatalytic Property Of Mo-Doped TiO₂ Nanomaterials

Titanium dioxide(Ti O2) has attracted considerable attention due to its excellent properties such as high photocatalytic activity, chemical stability and nontoxicity. However, the low utilization efficiency of solar energy is an important reason limiting its practical application. Doping Ti O2 and developing materials with special morphologier is a hotspot in visible light photocatalysis research.In this work, we prepared Mo doped Ti O2 nanoparticles as precursors. These particles were used to prepare Mo doped Ti O2 nanotubes. The as-prepared samples were characterized by X-ray diffraction(XRD), Diffuse reflectance UV-visible absorption spectra(UV-vis DRS), Scanning electron microscope(SEM), X-ray photoelectron spectra(XPS) and Transmission electron microscopy(TEM). The photocatalytic activity of nanoparticles and nanotubes was evaluated by photocatalytic degradation of methylene blue.Mo doped Ti O2 nanoparticles were synthesized by sol-gel method using tetrabutyl titanate and ammonium molybdate. The results showed that most of Mo6+ took the place of Ti4+ in the crystal lattice of Ti O2, which led to lattice distortion of Ti O2, inhibited the growth of crystallite size, suppressed the transformation from anatase to rutile. Mo doping narrowed the band gap(from 3.05 e V to 2.73 e V) and efficiently increased the optical absorption in visible region. When Mo doping amount was 2.0%, calcination temperature was 550℃, catalyst dosage was 0.5g/L, initial concentration of methylene blue was 20mg/L, the sample exhibited the highest photocatalytic activity, catalytic efficiency was up to 90.7% for 6h. Mo doping was shown to be an efficient method for degradation of methylene blue under visible light, especially under solar light, catalytic efficiency was up to 98.3% under solar light.Mo doped Ti O2 nanotubes were synthesized by hydrothermal method using Mo doped Ti O2 nanoparticles with highest photocatalytic activity. The results showed that the diameter of nanotubes was about 35 nm with a length ranging from several hundred nanometers. Nanotubes were still anatase at 650℃, which exhibited high thermal stability. However, rutile occurred at the same temperature in nanoparticles. The calcination temperature affected morphologies of nanotubes. From 400 to 450℃, it was observed that tubular structure was complete. With temperature increasing, nanotubes damaged. When temperature was up to 650℃, tubular structure was completely changed to particles. Mo doped Ti O2 nanotubes showed high photocatalytic activity with large specific surface area. Compared to particles, the degradation rate of methylene blue increased by 6%. After degradation experiments for three times, the efficiency of nanoparticles decreased by 10%, however, nanoparticles decreased by 5.2%, which showed that nanotubes performed better stability.