Effect of doping mode on the photocatalytic activities of Mo/TiO2

The thin films of photocatalyst, TiO2 doped by Mo6+ in different forms, were prepared by sol–gel method. The photocatalysts were characterized by X-ray diffraction (XRD), UV-Vis transmittance spectra and electrochemical impedance spectroscopy, and the photocatalytic activity was characterized by photocatalytic degradation of aqueous methyl orange under UV radiation. The results showed that the TiO2 doped by Mo6+ extend absorption edge and interfacial charge transfer resistance decrease. The photocatalytic activity of TiO2 doped by Mo6+ in bottom is much better than that of pure TiO2, those doped in surface, or those doped uniformly. The activity of TiO2 doped by Mo6+ in bottom mode at optimal concentration, 1 at.%, increased nearly two times than pure TiO2. The effects of doping modes on the photocatalytic activities were discussed in the terms of separateness of charge carriers that there maybe form barrier of carrier in bottom doping mode and then restraining the (e−–h+) pair recombination.