Preparation and characterization of a nano-sized Mo/Ti mixed photocatalyst

Nano-sized molybdenum-doped TiO2 (Mo/Ti) mixed oxide photocatalysts were pr epared with the Mo5+ content varying from 0 up to 2.5 mol%, to shift the ab sorption onset into the visible region and to enhance the efficiency of pho tocatalytic activity by retarding the (e(-)-h(+)) recombination. Prepared M o/Ti mixed oxides were characterized by ultraviolet and visible spectroscop y (UV/VIS), transmission electron microscopy-electron diffraction pattern ( TEM-EDP), X-ray diffraction(XRD), energy dispersive X-ray (EDAX) and X-ray photoelectron spectroscopy (XPS). Photonic efficiency was also investigated with the degradation rate of dichloroacetate (DCA) and light intensity mea sured by actinometry. TEM-EDP and XRD patterns showed that particles were i n the form of anatase with the diameter of ca. 4 nm. The appreciable red-sh ift in the UV/VIS absorption spectra was monitored at each preparation stag e - aging and dialyzing. The red-shift varied with addition of Mo, in the c ase of 2.5% Mo/Ti the UV/VIS absorption started at around 0.22 eV less than in nano-sized pure TiO2 (about 3.42 eV). EDAX verified that the amount of Mo in the prepared mixed oxides was as required, and XPS analysis revealed that Mo(V) existed in the TiO2 lattice. The measured photonic efficiency in creased to 0.28 with DCA at 0.5 mol% Mo, and then decreased as the Mo conte nt increased above 0.5 mol% Mo. This could be explained in terms of the cha nging prevailing phenomena - electron trapping and recombination - as the a mount of dopant increased in terms of the distance between the trapped site s of the charge carriers. (C) 2000 Elsevier Science B.V. All rights reserve d.