Characterization of Mo Doped TiO 2 and its Enhanced Photo Catalytic Activity Under Visible Light
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Characterization of Mo Doped TiO2 and its Enhanced Photo Catalytic Activity Under Visible Light L. Gomathi Devi Æ B. Narasimha Murthy
Received: 19 May 2008 / Accepted: 28 June 2008 / Published online: 16 July 2008 Springer Science+Business Media, LLC 2008
Abstract Transition metal doping into the TiO2 lattice can expand the response of these metal oxide nano particles to the visible region. In view of this, Mo6+ ion is doped into the TiO2 lattice in order to understand the mechanism of its photo response. The prepared photocatalysts were characterized by X-ray diffraction, UV–Visible absorption spectroscopy, UV–Visible diffuse reflectance spectroscopy, SEM, EDX, FTIR and BET specific surface area techniques. The characterization results have confirmed the incorporation of metal ions into TiO2 lattice. XRD analysis shows no change in crystal structure except a slight variation in crystallite size and elongation along the c-axis with increase in the concentration of the dopant. Diffuse reflectance measurements showed a shift in the band edge position to longer wavelengths and an extension of the absorption to the visible region. The photo degradation efficiencies of these catalysts were studied with Tebuconazole pesticide as model pollutant. Under UV light, undoped catalyst showed higher activity than doped catalyst. But in the case of visible light irradiation Mo doped TiO2 with intermediate dopant concentration of 0.06 atom % had the highest photocatalytic reactivity. This may be due to the narrowing of band gap so that it could effectively absorb the light of longer wavelength. The degradation path way was followed by UV–Visible spectroscopy. Keywords TiO2 Mo doped TiO2 Tebuconazole Visible light response Photocatalysis UV–Visible spectroscopy
L. Gomathi Devi (&) B. Narasimha Murthy Department of Chemistry, Bangalore University, Central College Campus, Dr. Ambedkar Veedhi, Bangalore 560 001, India e-mail: [email protected]
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1 Introduction Nanostructured semiconductors in heterogeneous photo catalysis have drawn considerable attention over the past few decades. This is due to their large surface area, high Redox potential of the phtogenerated charge carriers and selective reduction/oxidation of different classes of organic compounds. Among the semiconductors being studied, TiO2 is one of the most efficient photocatalyst under UV light irradiation [1, 2]. The basic principle of semiconductor photocatalysis involves the generation electron-hole pairs which serve as redox sources. These pairs are able to initiate oxidation and reduction reactions on the TiO2 photocatalyst [3]. The overall photo reactivity of TiO2 is determined by various factors such as generation of charge carriers, trapping of charge carriers and rate of formation of OH radicals. In photocatalysis process electron-hole pairs are generated in femtosecond time regime which must be trapped in order to avoid recombination which takes place around 100 nanoseconds. Duration of interfacial charge transfer and charge carrier re
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