• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.2883-2888
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• 2013

To enhance the power conversion efficiency of dye-sensitized solar cell (DSSC), the surface of titanium dioxide ($TiO_2$) photoelectrode was modified by hydroxylation treatment with $NH_4OH$ solution at $70^{\circ}C$ for 6 h. The $NH_4OH$ solutions of various concentrations were used to introduce the hydroxyl groups on $TiO_2$ surface. As the concentration of $NH_4OH$ was increased, the short-circuit current density ($J_{SC}$) value and conversion efficiency of solar cells were increased because the amount of adsorbed dye molecules on $TiO_2$ surface was increased. As a result of the surface modification to introduce hydroxyl groups, the concentration of adsorbed dye on the $TiO_2$ surface could be improved up to 32.61% without the changes of morphology, surface area and pore volume of particles. The morphology, the specific surface area, the pore volume and the chemical states of $TiO_2$ surface were characterized by using FE-SEM, $N_2$ adsorption-desorption isotherms and XPS measurements. The amount of adsorbed dye and the performance of fabricated cells were analyzed by using UV-Vis absorption spectroscopy and solar simulator.

• Korean Journal of Crystallography
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• v.8 no.2
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• pp.154-159
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• 1997

Hydorthemal coating technique has been sucessfully applied to improve oxidation resistance of graphite by forming rutile-TiO2 layer. Hydrothermal treatment of graphite in 0.2M TiCl4 aquous solution at 35℃ resulted in improved water wettability due to the formation of surface-modifying TiO2. The amount of TiO2 increased with temperature. In the presence of surface TiO2 layer, weight loss was reduced by 30%, while the initiation temperature of oxidation was lowered by 30℃.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.415-418
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• 2014

Phenyltrimethoxysilane (PTMS) was anchored onto the sensitized $TiO_2$ nanoparticles. This insulating molecular layer effectively inhibited the charge recombination at the interface of $TiO_2$/electrolyte in the dye-sensitized solar cells (DSCs) without sacrificing the dye-loading capacity of the nanocrystalline $TiO_2$. DSCs using PTMS-modified $TiO_2$ exhibited a short-circuit current ($J_{SC}$) of $15.9mA/cm^2$, an open-circuit voltage ($V_{OC}$) of 789 mV, and a fill factor (FF) of 68.2%, yielding an overall conversion efficiency (${\eta}$) of 8.55% under $100mW/cm^2$ illumination. The resulting cell efficiency was improved by ~10% as compared with the reference cell.

• Korean Journal of Materials Research
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• v.20 no.5
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• pp.246-251
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• 2010

The composite photocatalysts of a Fe-modified carbon nanotube (CNT)-$TiO_2$ were synthesized by a two-step sol-gel method at high temperature. Its chemical composition and surface properties were investigated by BET surface area, scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD) and ultraviolet-visible (UV-Vis) spectroscopy. The results showed that the BET surface area was improved by modification of Fe, which was related to the adsorption capacity for each composite. Interesting thin layer aggregates of nanosized $TiO_2$ were observed from TEM images, probably stabilized by the presence of CNT, and the surface and structural characterization of the samples was carried out. The XRD results showed that the Fe/CNT-$TiO_2$ composites contained a mix of anatase and rutile forms of $TiO_2$ particles when the precursor is $TiOSO_4{\cdot}xH_2O$ (TOS). An excellent photocatalytic activity of Fe/CNT-$TiO_2$ was obtained for the degradation of methylene blue (MB) under visible light irradiation. It was considered that Fe cation could be doped into the matrix of $TiO_2$, which could hinder the recombination rate of the excited electrons/holes. The photocatalytic activity of the composites was also found to depend on the presence of CNT. The synergistic effects among the Fe, CNT and $TiO_2$ components were responsible for improving the visible light photocatalytic activity.

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.61.1-61
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• 2002

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.1116-1120
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• 2002

Using thermal hydrolysis and hydrothermal treatment, photocatalytic $TiO_2$ powders were synthesized. During the synthesis, the addition of other transition metals such as iron, copper, etc., affected the photocatalytic capability of synthesized powders, and enabled the activation by visible light. To enhance photocatalytic capacity of gas phase decomposition, the rate-determining adsorption rate of pollutant gases were improved via surface modification of $TiO_2$ powders. The surface modifiers were implanted using mechanochemical synthesis of dopants and photocatalytic powders.

• Bulletin of the Korean Chemical Society
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• v.22 no.12
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• pp.1371-1374
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• 2001

Metal doping was adopted to modify TiO2 (P-25) and enhance the photocatalytic degradation of harmful cyanides in aqueous solution. Ni, Cu, Co, and Ag doped TiO2 were found to be active photocatalysts for UV light induced degradation of aqueous cyanides generating cyanate, nitrate and ammonia as main nitrogen-containing products. The photoactivity of Ni doped TiO2 was greatly affected by the state of Ni, that is, the crystal size and the degree of reduction of Ni. The modification effects of some mixed oxides, that is, Ni-Cu/TiO2 were also studied. The activity of Ni-Cu/TiO2 for any ratio of Cu/Ni was higher than that of Ni- or Cu-doped TiO2, and the catalyst at the Cu/Ni ratio of 0.3 showed the highest activity for cyanide conversion.

• Applied Chemistry for Engineering
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• v.1 no.1
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• pp.35-43
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• 1990

A series of $TiO_2-SiO_2$catalysts were prepared by coprecipitation from the mixed solution of titanium tetrachloride and sodium silicate. Some of the samples were treated with 1N $H_2SO_4$ and used as modified catalysts. The catalytic activities of modified catalysts were higher than those of unmodified catalysts, and the effect of modification on the catalytic activity was higher for 2 - propanol dehydration than for cumene dealkylation. The catalytic activity of unmodified catalysts was correlated with their acid amount for the above two reactions. As $TiO_2-SiO_2$ catalysts had relatively large amount of weak acid sites and small amount of strong acid sites, the catalytic activity for 2 - propanol dehydration was higher than that for cumene dealkylation. The effect of modification on catalytic activity increased with increasing $TiO_2$content of the catalysts. Actually, $92-TiO_2-SiO_2/SO_4{^2}$had the highest increment in catalytic activity and $10-TiO_2-SiO_2/SO_4{^2}$had the lowest increment for the 2 - propanol dehydration.

• Applied Chemistry for Engineering
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• v.20 no.4
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• pp.402-406
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• 2009

$TiO_2$ thin films were surface-modified with atmospheric plasma and their photocatalytic activities were evaluated. The films were deposited on glass plates by dip-coating in a $TiO_2$ sol-gel solution and sintered at various temperatures for various times. Nitrogen plasma was used for the modification and the experiments were carried out varying operational parameters such as discharge power and treatment time. Photocatalytic activity was evaluated based on the degradation efficiency of methylene blue (MB) under irradiation of UV-A and fluorescent light. According to XPS analysis, a little amount of nitrogen was found to be doped in the film surface after the modification. As a result, photocatalytic activity increased under irradiation of UV-A and fluorescent light, especially fluorescent light.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1237-1240
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• 2014