AbstractA set of transition metal doped nanosized TiO2 particles with anatase structure were synthesized by the pulverization method and their ability to photocatalytically degrade the dye Alizarin Red S was investigated. Characterization of the Zr-, Co- and Mo-doped photocatalysts was conducted with the aid of XRD, SEM, EDX, TEM, BET and spectral analysis. X-ray diffraction patterns did not reflect the appearance of any peaks due to dopants, however dopants were observed in SEM-EDX analysis. Particle sizes were in the range of 25 nm as per TEM and XRD analysis. Upon doping, a prominent decrease in surface area was observed. The percentage composition of each of the dopants was confirmed by EDX analysis. Doped samples depicted many mid-bands in the Kubelka Munk plots due to d-d transition of dopants. Experiments were conducted to compare the photocatalytic activity under identical UV and solar light exposure. Zr-doped TiO2 at the molecular scale exhibited better photocatalytic activity in degradation of Alizarin, with a lower band-gap energy that can respond to visible light. However, Co- and Mo-doped TiO2 appeared to suppress the photoactivity. A rise in the number of mid-bands causing effective separation or recombination of charge carriers strongly influences the rate of the degradation process.
Transition metal doped TiO2 (Ni, Fe, Cu) and nanocomposite TiO2 powders with rutile
phase were synthesized by mechanical alloying and heat treatment, and were characterized by
XRD, TEM, UV-DRS, and PL (Photoluminescence). Photocatalytic activity was also investigated
with the degradation rate of 4-chlorophenol and measured by total organic carbon analyzer. TEMEDP
and XRD patterns showed that the transition metal doped powders (only alloyed powder) were
in the form of rutile phase with the particle size of 20-30 nm. The average grain size of transition
metal doped powders was in the range of less than 10 nm. However, after heat treatment, the
alloyed powder formed composite of the titanate and rutile phase. The UV-DRS and PL
investigation showed that Ni doped 8 wt% nanocomposite TiO2 had the higher wavelength range
(600-660 nm) (2.0-1.9 eV) than that of the commercial P-25 powder(380-400 nm) by Degussa Co.
indicating that the Ni 8 wt% doped nanocomposite TiO2 shifted the absorption into the visible light
region and thus, enhanced the photocatalytic activity. Further, these results agreed well with TOC
investigation. Formation of titanate in transition metal doped TiO2 due to heat treatment was found
to control the grain growth of nano-sized TiO2 and to enhance its thermal stability at high
Transition metal-doped TiO2 powders as a photocatalyst were prepared by sol-gel process and Sb, Bi and Nb were introduced into them as dopants. The photocatalytic behaviors of the doped TiO2 powder were studied as a function of dopant, doping concentration and preparation conditions. X-ray diffraction, FT-Raman, B.E.T. and scanning electron microscopy were applied for structural and microstructural studies. Optical properties of the doped TiO2 powders were studied by UV-Visible Spectrometer and photocatalytic activity of the doped TiO2 was characterized in terms of the degradation of 1,4-dichlorobenzene. X-ray difraction analysis showed that doping with a transition metal ion suppresses anatase-to-rutile phase transition compared with the pure TiO2. The Sb and Nb-doped TiO2 powders did not exhibit any other diffraction peaks except those belonging to TiO2. On the other hand, a diffraction peak of Bi4Ti3O12 appears for 5 at.% Bi-doped samples. All of the doped TiO2 powders had higher specific surface area than undoped TiO2. Surface area increased with increasing dopant concentration depending on the dopant, from 33.9 m2/g to 55.4m2/g. The UV-visible absorption spectra of doped samples were red-shifted by 20~50nm according to the doping level. Also transition metal doped TiO2 powders exhibited better photocatalytic activity than the undoped TiO2. The increase in photoactivity is probably due to the increase in the interfacial electron transfer, red shifts, and better crystallinity.