Microwave photocatalysis III. Transition metal ion‐doped TiO2thin films on mercury electrodeless discharge lamps: preparation, characterization and their effect on the photocatalytic degradation of mono‐chloroacetic acid and Rhodamine B

Abstract

AbstractBACKGROUND:Mercury electrodeless discharge lamps (Hg‐EDLs) were used to generate UV radiation when exposed to a microwave field. EDLs were coated with doped TiO2in the form of thin films containing transition metal ions Mn+(M = Fe, Co, Ni, V, Cr, Mn, Zr, Ag). Photocatalytic degradation of mono‐chloroacetic acid (MCAA) to HCl, CO2, and H2O, and decomposition of Rhodamine B on the thin films were investigated in detail.RESULTS:Polycrystalline thin doped TiO2films were prepared by dip‐coating of EDL via a sol–gel method using titaniumn‐butoxide, acetylacetone, and a transition metal acetylacetonate. The films were characterized by Raman spectroscopy, UV/Vis absorption spectroscopy, X‐ray photoelectron spectroscopy (XPS), electron microprobe analysis and by atomic force microscopy (AFM). The photocatalytic activity of doped TiO2films was monitored in the decomposition of Rhodamine B in water. Compared with the pure TiO2film, the UV/Vis spectra of V, Zr and Ag‐doped TiO2showed significant absorption in the visible region, and hence the photocatalytic degradation of MCAA had increased. The best apparent degradation rate constant (0.0125 min−1), which was higher than that on the pure TiO2film by a factor of 1.7, was obtained with the Ag(3%)/TiO2photocatalyst. The effect of doping level of vanadium acetylacetonate on the photocatalytic efficiency of the V‐doped TiO2was determined.CONCLUSIONS:Transition metal ion‐doped TiO2thin films showed significant absorption in the visible region. The metal doped TiO2photocatalyst (with an appropriate amount of V, Zr and Ag) on the Hg‐EDLs increased the degradation efficiency of MCAA in a microwave field. Copyright © 2009 Society of Chemical Industry