• Bulletin of the Korean Chemical Society
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• v.27 no.9
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• pp.1423-1428
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• 2006

In this study, we have prepared pitch binded AC (activated carbon)/$AC/TiO_2$ composites photocatalysts through carbon tetrachloride solvent method. The developed samples were characterized with surface properties, structural crystallinity between AC and $AC/TiO_2$, elemental identification and photocatalytic activity. The results of the textural surface properties demonstrate that there are slight increases in the BET surface area and adsorbed volume from adsorption isotherm of composite samples with increasing of the amount of AC. The SEM results present to the characterization of porous texture on the pitch/AC/$AC/TiO_2$ composites and homogenous compositions in the particle for all the materials used. From XRD data, a weak and broad carbon peak of graphene remained rutile peaks kept with anatase structure were observed in the X-ray diffraction patterns for the pitch/AC/$AC/TiO_2$ composites. The EDX spectra show the presence of C, O and S with strong Ti peaks. Most of these samples are richer in carbon and major Ti metal than any other elements. Finally, the excellent photocatalytic activity of the pitch/AC/$AC/TiO_2$ composites between relative concentration ($c/c_o$) of MB and UV irradiation time could be attributed to the both effects between photocatalysis of the supported $AC/TiO_2$ and adsorptivity of the two kinds of carbons.

• Journal of Powder Materials
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• v.25 no.3
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• pp.226-231
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• 2018

F-containing $TiO_2$ nanopowders are synthesized using simple wet processes (precipitation-based and hydrothermal) from ammonium hexafluorotitanate (AHFT, $(NH_4)_2TiF_6$) as a precursor to apply as a photocatalyst for the degradation of rhodamine B (RhB). The surface properties of the prepared samples are evaluated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The results confirm that the synthesized anatase $TiO_2$ has sphere-like shapes, with numerous small nanoparticles containing fluorine on the surface. The photocatalytic activity of F-containing $TiO_2$ compared with F-free $TiO_2$ is characterized by measuring the degradation of RhB using a xenon lamp. The photocatalytic degradation of F-containing $TiO_2$ exhibits improved photocatalytic activity, based on the positive effects of adsorbed F ions on the surface.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.11
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• pp.1019-1024
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• 2009

Visible-light-active $TiO_2-_xN_x$ nanoparticles with a homogeneous anatase crystalline structure were successfully prepared through a hydrolysis of $TiCl_4$ with ammonia solution. The samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), $N_2$-sorption, and UV-vis diffuse reflectance spectra (DRS) techniques. The light absorption onset shifted from 390 nm on pure $TiO_2$ to the visible region at 530 nm on nitrogen-doped $TiO_2$. A clear decrease in the band gap was deduced from the DRS results. The photocatalytic activity was evaluated from the photodegradation of congo red solution under visible light irradiation. The photocatalyst showed the highest photocatalytic activity at an optimal value of nitrogen doping concentration. This was suggested that the nitrogen doping should have an important effects on the improvement of photocatalytic activity.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2849-2853
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• 2010

A method to improve the photocatalytic activity of titanium dioxide by modification with a sensitizer and a metal oxide is proposed. To achieve this goal, we used metal oxides as dopants. In particular, $CaWO_4$ and $Gd_2O_2S$:Tb were used because their 2.6 eV and 2.2 eV band gap energy and optical properties have a large positive effect on photocatalysis. The improvement in the photocatalytic activity of $TiO_2$ modified with $Gd_2O_2S$:Tb under ultraviolet light irradiation is described in a previous study. The present work focuses on the sensitization of metal oxide-modified $TiO_2$. Having observed the ultraviolet-visible absorption spectra of 3,4,9,10-Perylenetetracarboxylic diimide in the wide visible-light region from 400 nm to 650 nm and the broad peaks in its photoluminescence spectra at 695 nm and 717 nm, we decided to use this perylene dye to sensitize modified $TiO_2$ to enhance its activity as a visible-light harvesting photocatalyst. We also explored the positive effects thin-film surface changes stemming from ultraviolet pre-treatment have on photocatalytic activity. Finally, we subjected several metal oxide-modified $TiO_2$ products sensitized by the perylene dye to ultraviolet pre-treatment, obtaining the most active photocatalysts.

• Environmental Engineering Research
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• v.23 no.2
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• pp.181-188
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• 2018

Photocatalytic oxidation in the presence of Fe-doped, Zn-doped or Fe-Zn co-doped $TiO_2$ was used to effectively decompose humic acids (HAs) in water. The highest HAs removal efficiency (65.7%) was achieved in the presence of $500^{\circ}C$ calcined 0.0010% Fe-Zn co-doped $TiO_2$ with the Fe:Zn ratio of 3:2. The initial solution pH value, inorganic cations and anions also affected the catalyst photocatalytic ability. The HAs removal for the initial pH of 2 was the highest, and for the pH of 6 was the lowest. The photocatalytic oxidation of HAs was enhanced with the increase of the $Ca^{2+}$ or $Mg^{2+}$ concentration, and reduced when concentrations of some anions increased. The inhibition order of the anions on $TiO_2$ photocatalytic activities was $CO{_3}^{2-}$ > $HCO_3{^-}$ > $Cl^-$, but a slightly promotion was achieved when $SO{_4}^{2-}$ was added. Total organic carbon (TOC) removal was used to evaluate the actual HAs mineralization degree caused by the $500^{\circ}C$ calcined 0.0010% Fe-Zn (3:2) co-doped $TiO_2$. For tap water added with HAs, the $UV_{254}$ and TOC removal rates were 57.2% and 49.9%, respectively. The $UV_{254}$ removal efficiency was higher than that of TOC because of the generation of intermediates that could significantly reduce the $UV_{254}$, but not the TOC.

• Korean Journal of Materials Research
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• v.22 no.8
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• pp.439-444
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• 2012

To compare the photocatalytic performances of titania for purification of waste water according to applied voltages and doping, $TiO_2$ films were prepared in a 1.0 M $H_2SO_4$ solution containing $NH_4F$ at different anodic voltages. Chemical bonding states of F-N-codoped $TiO_2$ were analyzed using surface X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the co-doped $TiO_2$ films was analyzed by the degradation of aniline blue solution. Nanotubes were formed with thicknesses of 200-300 nm for the films anodized at 30 V, but porous morphology was generated with pores of 1-2 ${\mu}m$ for the $TiO_2$ anodized at 180 V. The phenomenon of spark discharge was initiated at about 98 V due to the breakdown of the oxide films in both solutions. XPS analysis revealed the spectra of F1s at 684.3 eV and N1s at 399.8 eV for the $TiO_2$ anodized in the $H_2SO_4-NH_4F$ solution at 180 V, suggesting the incorporation of F and N species during anodization. Dye removal rates for the pure $TiO_2$ anodized at 30 V and 180 V were found to be 14.0% and 38.9%, respectively, in the photocatalytic degradation test of the aniline blue solution for 200 min irradiation; the rates for the F-N-codoped $TiO_2$ anodized at 30 V and 180 V were found to be 21.2% and 65.6%, respectively. From the results of diffuse reflectance absorption spectroscopy (DRS), it was found that the absorption edge of the F-N-codoped $TiO_2$ films shifted toward the visible light region up to 412 nm, indicating that the photocatalytic activity of $TiO_2$ is improved by appropriate doping of F and N by the addition of $NH_4F$.

• Journal of Welding and Joining
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• v.21 no.4
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• pp.46-55
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• 2003

TiO$_2$-WO$_3$(8.2wt%) coatings were prepared by the APS (Atmospheric Plasma Spraying) process to clarify the relationship between the process parameters(H$_2$ gas flow rate of plasma 2nd gas and spraying distance) of the APS coating and photo-decomposition efficiency kinetics of the MB(methylene blue) aqueous solution decomposition and to understand the effect of addition of WO$_3$ on photocatalytic properties of TiO$_2$ sprayed coating. Further, the temperature and velocity of flying particles were measured by DPV-2000 to investigate the relationship between microstructure of coatings and process parameters. Properties of coatins were investigated by XRD, SEM, XPS, RAMAN, UV/VIS spectrometer. In case of the TiO$_2$-WO$_3$(8.2wt%) coating, it had a lower anatase fraction than that of pure-TiO$_2$ coatings because of flying in the higher temperature plasma plume by the heavy weight of TiO$_2$, WO$_3$. And, when WO$_3$ added powders were spayed, the doping effects of W ions substituted into the Ti ion sites was not occured during melting and solidification cycles of spraying. It was found that the addition of WO$_3$ was ineffective effective on increasing photo-decomposition efficiency of TiO$_2$ sprayed coating.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1998.11a
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• pp.73-74
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• 1998

• Transactions on Electrical and Electronic Materials
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• v.12 no.2
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• pp.68-71
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• 2011

[ $Ti_{1-x}W_xO_{2-y}$ ]solid solutions with compositions of x = 0.01(TW-1), x = 0.02(TW-2), x = 0.03(TW-3) and x = 0.04(TW-4) were prepared at 1,073 K in air under atmospheric pressure. All the solutions exhibited tetragonal symmetries. Nonstoichiometric chemical formulas have been obtained from oxidation-reduction titration and the partial substitution of $W^{6+}$ ions mainly caused the formation of $Ti^{3+}$ ion, rather than oxygen excess. Resistivities of the samples were highly dependent on humidity. The increase of the W amount resulted in an increase of $Ti^{3+}$ content, decrease of resistivity values and finally degradation of photocatalytic activities.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.569-572
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• 2003

Titanium dioxide ($TiO_2$) nanoparticles were prepared by the oxidation of titanium tetrachloride ($TiCl_4$) in a diffusion flame reactor. The average diameter of particles was 15 to 30 nm and mass fraction of anatase ranged from $40\;to\;80\%$. Effects of particle size and phase composition of those $TiO_2$ nanoparticles on photocatalytic properties such as decomposition of methylene blue and bacteria gas were investigated. The degree of decomposition of methylene blue by the $TiO_2$ nanoparticles under the illumination of the black light was directly proportional to the anantase mass fraction, but inversely to the particle size. The decomposition of bacteria by the $TiO_2$ nanoparticles under the illumination of the fluorescent light showed the same trend as in the case of the methylene blue.