Photoinduced hydroxyl radical and photocatalytic activity of samarium-doped TiO2 nanocrystalline

School of Resources Processing and Bioengineering, Central South University, Changsha 410083, China.
Journal of Hazardous Materials (Impact Factor: 4.33). 02/2008; 150(1):62-7. DOI: 10.1016/j.jhazmat.2007.04.045
Source: PubMed

ABSTRACT Sm(3+)-doped TiO(2) nanocrystalline has been prepared by sol-gel auto-combustion technique and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, and also UV-vis diffuse reflectance spectroscopy (DRS). These Sm(3+)-doped TiO(2) samples were tested for methylene blue (MB) decomposition and *OH radical formation. The analysis of *OH radical formation on the sample surface under UV irradiation was performed by fluorescence technique with using terephthalic acid, which readily reacted with *OH radical to produce highly fluorescent product, 2-hydroxyterephthalic acid. It was observed that the presence of Sm(3+) ion as a dopant significantly enhanced the photocatalytic activity for MB degradation under UV light irradiation because both the larger specific surface area and the greater the formation rate of *OH radical were simultaneously obtained for Sm(3+)-doped TiO(2) nanocrystalline. The adsorption experimental demonstrated that Sm(3+)-TiO(2) had a higher MB adsorption capacity than undoped TiO(2) and the adsorption capacity of MB increased with the increase of samarium ion content. The results also indicated that the greater the formation rate of *OH radical was, the higher photocatalytic activity was achieved. In this study, the optimum amount of Sm(3+) doping was 0.5 mol%, at which the recombination of photo-induced electrons and holes could be effectively inhibited, the highest formation rate of *OH radicals was, and thereby the highest photocatalytic activity was achieved.

Download full-text


Available from: Zhichun Si, Jul 28, 2015
  • Source
    • "The lanthanide ions with 4f electron configurations into TiO 2 lattice can act as an electron reservoir to trap electrons and significantly increase the separation rate of generated electron–hole pairs, resulting in the improvement of the catalytic activity [27] [28] [29]. On the other hand, lanthanide ions doping can enhance the light sensitivity of catalyst and provide a means to concentrate the organic pollutant at the catalyst surface [30] [31]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In this work, pure TiO2 and samarium, cerium mono-doped and co-doped TiO2 catalysts were synthesized by an ultrasonic-assisted sol-gel method and their sonocatalytic efficiency studied toward removal of Methyl Orange as a model organic pollutant from the textile industry. The relationship of structure and sonocatalytic performance of catalysts was established by using various techniques, such as XRD, TEM, SEM, EDX, DRS, and PL. A comparison on the removal efficiency of sonolysis alone and sonocatalytic processes was performed. The results showed that the samarium, cerium co-doped TiO2 catalyst with narrower band gap energy and smaller particle size leads to a rapid removal of pollutant. It was believed that Sm(3+) and Ce(4+) ions can serve as superficial trapping for electrons at conduction band of TiO2 and prolonged the lifetime of electron-hole pairs. Finally, the effect of synthesis and operational variables on the sonocatalytic activity of co-doped TiO2 catalyst was studied and optimized using response surface methodology as a statistical technique. The results showed that the maximum removal efficiency (96.33%) was achieved at the optimum conditions: samarium content of 0.6wt%, cerium content of 0.82wt%, initial pollutant concentration of 4.31mgL(-1), catalyst dosage of 0.84mgL(-1), ultrasonic irradiation power of 700W, and irradiation time of 50min. Copyright © 2015 Elsevier B.V. All rights reserved.
    Ultrasonics Sonochemistry 02/2015; 26:281–292. DOI:10.1016/j.ultsonch.2015.02.001 · 4.32 Impact Factor
  • Source
    • "The enhanced production of HCHO using P25-500 and other catalytic reaction under direct sunlight irradiation was confirmed by hydroxyl radical ( • OH) determination during the course of the reaction using fluorescence technique with terephthalic acid as a probe molecule (Ishibashi et al. 2000; Yu et al. 2009; Xiao et al. 2008). The result revealed that (Fig. 12a– e), the fluorescence intensity at 425 nm is increased with increase in the direct sunlight irradiation time for all the catalytic reaction. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The present study focused on photocata-lytic oxidation of methanol to formaldehyde using nanocrystalline TiO 2 (Degussa P-25) photocatalyst calcined at different temperature having different ratio of anatase (A)–rutile (R) phase composition under direct sunlight irradiation. The calcined nanocrystal-line TiO 2 was characterized using powder X-ray diffraction, N 2 adsorption, scanning electron micros-copy, transmission electron microscopy, Fourier transform infrared, and UV–Visible diffuse reflec-tance spectroscopy techniques. The determination of hydroxyl radical formation during the course of the reaction was carried out using fluorescence technique with terephthalic acid as a probe molecule. The photocatalytic activity of catalysts was evaluated by methanol oxidation under direct sunlight irradiation and activity was compared with pure anatase TiO 2. The result revealed that nanocrystalline TiO 2 (P-25) calcined at 500 °C displays higher photocatalytic activity and the order of rate of HCHO formation is P25-500 (A74 %:R26 %) [ P25 (A80 %:R20 %) [ AT (A100 %) [ P25-600 (A12 %:R88 %) [ P25-700 (R100 %). The result also infers that TiO 2 with mixed phase exhibit higher photocatalytic activity than TiO 2 with pure anatase or rutile phase. The rapid transfer of photogenerated electron from rutile to anatase leads to increase in the charge separation and enhances the photocatalytic activity under direct sunlight irradiation. Effect of operational parameters like amount of catalyst and effect of reaction atmosphere have been investigated on the photocatalytic oxidation of methanol under direct sunlight irradiation.
    Journal of Nanoparticle Research 11/2014; 16(11). DOI:10.1007/s11051-014-2713-7 · 2.28 Impact Factor
    • "Both these photoinduced species have the potential to initiate several redox reactions with other entities present on the surface of photocatalyst. The various chemical reactions in UV-visible light illuminated atrazine (ATZ) solutions containing photocatalyst are summarized below (Xiao et al., 2008; Vijayabalan et al., 2009; Yu et al., 2010 "
    [Show abstract] [Hide abstract]
    ABSTRACT: Conventional titanium dioxide (TiO2) materials can be activated only by ultraviolet (UV) light, which is only 4–5% of the whole solar spectrum. As a result, visible light (vis)–active TiO2-based photocatalysts have recently received significant attention in the field of TiO2 photocatalytic treatment and purification of water and air. This study reports the preparation of UV-visible light–active phosphorous (P)-doped, fluorine (F)-doped, and PF–co-doped anatase TiO2 nanoparticles via an innovative sol-gel method. Prepared nanoparticles were characterized by UV-vis diffuse reflectance spectroscopy, X-ray diffraction analysis, Raman spectroscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy (FTIR), and porosimetry analysis. Synthesized materials exhibited improved structural properties, including high surface area, small crystallite size, reduced band gap energy, mesoporous structure, and high porosity. Due to doping with P and F, light absorption of TiO2 in the visible light region was efficiently enhanced with effective band gap energy of 2.70 eV. Brunauer-Emmett-Teller (BET) surface area for PF–co-doped, P-doped, F-doped, and reference TiO2 nanoparticles was 212.0, 175.0, 88.8, and 79.7 m2/g, respectively. PF–co-doped TiO2 showed the highest photocatalytic degradation of atrazine, which could be attributed to the beneficial effects including small crystallite size, high BET surface area, and light absorption in UV-visible region, induced by co-doping of TiO2 with P and F. Finally, reaction intermediates were determined, which confirms the photocatalytic degradation of atrazine using the synthesized catalysts under UV-visible light illumination.
    Environmental Engineering Science 07/2014; 31(7):435-446. DOI:10.1089/ees.2013.0486 · 0.93 Impact Factor
Show more