• Journal of the Korean Ceramic Society
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• v.56 no.3
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• pp.284-290
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• 2019

Ternary MoS₂/graphene (G)-TiO₂ photocatalysts were prepared by a simple hydrothermal method. The morphology, phase structure, band gap, and catalytic properties of the prepared samples were investigated by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, UV-vis spectrophotometry, and Brunauer-Emmett-Teller surface area measurement. The H₂ production efficiency of the prepared catalysts was tested in methanol-water mixture under visible light. MoS₂/G-TiO₂ exhibited the highest activity for photocatalytic H₂ production. For 5 wt.% and 1 wt.% MoS₂ and graphene (5MT-1G), the production rate of H₂ was as high as 1989 µmol^-1h^-1. The catalyst 5MT-1G showed H₂ production activity that was ~ 11.3, 5.6, and 4.1 times higher than those of pure TiO₂, 1GT, and 5MT, respectively. The unique structure and morphology of the MoS₂/G-TiO₂ photocatalyst contributed to its improved hydrogen production efficiency under visible light.

• Journal of Institute of Convergence Technology
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• v.8 no.1
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• pp.21-25
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• 2018

We developed nano-porous $TiO_2-SiO_2$ composites (commercial name : PTI, porous titania insulator) with low thermal conductivity as thermal insulating material as well as function of photocatalyst. The objectives of this paper are, firstly, to evaluate of the thermal conductivity of the PTI powder in the temperature range from -160 to $250^{\circ}C$, secondly to evaluate of thermal conductivities of insulation materials that is applied PTI powder. The structure of the PTI powder that has the pores size of 20-30 nm and the particle diameter of 2-10 nm. The PTI had a high surface area of $400m^2/g$ and a mean pore size of $45{\AA}$, which was fairly uniform. The thermal conductivity was measured by GHP(guarded hot plate) method and HFM(heat flux method). The PTI structure is a three-dimensional network nano-structures composed by a pearl-necklace that involved a precious stone in the center of the necklace. The thermal conductivities of PTI-PX powder by the GHP and HFM were 0.0366 W/m.K, 0.0314 W/m.K at $20^{\circ}C$, respectively. This is similar to values that are proportional to the square of the absolute temperature of the thermal conductivity of static air. The thermal conductivities of insulating sheets coated with PTI powder were similar results with that of the PTI powder.

• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1034-1042
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• 1996

Various $TiO_2-SiO_2$ composite powders were prepared by the modified sol-gel method using 1-dodecanol as DCCA (Dryng Control Chemical Additive ). Their characterizations were carried out and their photocatalytic catalysis was examined on the evolution reaction of hydrogen. The weight losses at $500^{\circ}C$ of only $TiO_2$ and $SiO_2$ powders were 33. 0wt% and 42.5wt%, respectively, and those of the $TiO_2/SiO_2$ powders ($TiO_2/SiO_2=25/75$, 50/50 and 75/25) were about $70.0{\pm}3.0wt%$. The released substances from the powders were almost organic matters. The as-prepared powders except only $TiO_2$ powder were amorphous. Transformation of anatase to rutil was hindered by $SiO_2$ component and the crystallinity of anatase was decreased with increasing $SiO_2$ contents. The as-prepared powders were bulky states. By heating at $600^{\circ}C$ for 1 hr $TiO_2-SiO_2$ powders ($TiO_2=100%$, $TiO_2/SiO_2=75/25,\;50/50$) showed agglomerates consisted of particles in submicron, but those of $TiO_2/SiO_2=25/75$ and $SiO_2=100%$ were still bulky states. Specific surface area of the powders heat-treated at $600^{\circ}C$ for 1hr was increased with $SiO_2$ concents and their pore sizes were also depended on $SiO_2$ contents. The photocatalytic activity of $TiO_2/SiO_2=75/25$ heat-treated at $600^{\circ}C$ for 1hr was 0.240mo1/h.g-cat as $H_2$ evolution rate. This value was about 2.0 times that of P-25(Degussa P-25) as a standard photocatalyst.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.E3
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• pp.121-127
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• 2003

The characteristics of heterogeneous photocatalytic decomposition were investigated at low concentration level of $O_3$on TiO$_2$for various operating parameters such as: loaded catalyst weight (0∼4 mg/$\textrm{cm}^2$), initial concentration of $O_3$(0.06∼10.0 ppm), gas flow rate (1.0 ∼ 2.5ι/min), and relative humidity (0∼80%). This study was conducted using a flow-type reactor at room temperature. Three kinds of pure TiO$_2$(P25, ST -01, and E- 23) were employed as photocatalyts. It was found that $O_3$removal ratio was identical, regardless of the loaded TiO$_2$weight in the range from 0.5 to 4.0 mg/$\textrm{cm}^2$. It was also found that higher initial ozone concentration results in greater oxidation rate of ozone and experimental data show kinetically a good agreement with Langmur-Hinshelwood kinetic model. We also observed that the removal ratio of $O_3$increases linearly with the increasing flow rate and also with the increasing relative humidity for each catalyst.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.04a
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• pp.307-308
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• 2002

최근 들어 지구환경의 보전 필요성이 그 어느 때보다도 강하게 제기되면서 대류권 내에서 진행되는 광화학적 대기오염 현상과 그에 따른 오존농도의 증가에 대해 많은 관심이 집중되고 있다 광화학적 대기오염현상이란 대기중의 휘발성 유기화합물(Volatile Organic Compounds VOCs)과 질소산화물(NOx)이 햇빛 내의 자외선에 의해 반응하면 오존, 알데히드, peroxyacetyl nitrate 등과 같은 2차 오염물질인 광화학 산화물을 생성하는 것을 의미하는데 이 광화학 산화물은 생물체에 악영향을 주고 아울러 성층권의 오존층을 파괴하여 궁극적으로는 지구 온난화 현상의 원인이 되고 있다. (중략)

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.108-114
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• 2018

Degradations of durability and aesthetic performance in concrete happen during service life due to surface deterioration and dirt stains. Recently, many researches have been performed on self-cleaning and surface enhancement through surface impregnant using photocatalytic reaction with VOCs(Volatile Organic Compounds) removal. This paper is for preliminary study on surface impregnation with silicate and photocatalysis - $TiO_2$. For the work, two types of silicate based impregnants(CS - Coloidal Silica and SC - Sodium Alumina Silicate) are considered. Several tests for viscosity and surface tension are performed, and pull-off test on impregnated concrete is performed. For the surface impregnated concrete, $TiO_2$ is absorbed through submerging and spraying conditions. Through compressive strength test and SEM analysis, it is evaluated that spraying $TiO_2$ on surface impregnated concrete after 30min. of drying period is very effective both for strength enhancement and surface densification.

• Journal of Sensor Science and Technology
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• v.31 no.2
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• pp.102-106
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• 2022

Currently, the demand for real-time monitoring of water quality has increased dramatically. Total organic carbon (TOC) analysis is a suitable method for real-time analysis compared with conventional biochemical oxygen demand (BOD) and chemical oxygen demand (COD) methods in terms of analysis time. However, this method is expensive because of the complicated internal processes involved. The photocatalytic titanium dioxide (TiO2)-based TOC method is simpler as it omits more than three preprocessing steps. This is because it reacts only with organic carbon (OC) without extra processes. We optimized the rate between the TiO2 photocatalyst and binder solution and the TiO2 concentration. The efficiency was investigated under 365 nm UV exposure onto a TiO2 coated substrate. The optimized conditions were sufficient to apply a real-time monitoring system for water quality with a short reaction time (within 10 min). We expect that it can be applied in a wide range of water quality monitoring industries.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.1-7
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• 2012

In this article, I will introduce recent developments of environmental-friendly materials fabricated using atomic layer deposition (ALD). Advantages of ALD include fine control of the thin film thickness and formation of a homogeneous thin fim on complex-structured three-dimensional substrates. Such advantages of ALD can be exploited for fabricating environmental-friendly materials. Porous membranes such as anodic aluminum oxide (AAO) can be used as a substrate for $TiO_2$ coating with a thickness of about 10 nm, and the $TiO_2$-coated AAO can be used as filter of volatile organic compound such as toluene. The unique structural property of AAO in combination with a high adsorption capacity of amorphous $TiO_2$ can be exploited in this case. $TiO_2$ can be also deposited on nanodiamonds and Ni powder, which can be used as photocatalyst for degradation of toluene, and $CO_2$ reforming of methane catalyst, respectively. One can produce structures, in which the substrates are only partially covered by $TiO_2$ domains, and these structures turns out to be catalytically more active than bare substrates, or complete core-shell structures. We show that the ALD can be widely used not only in the semiconductor industry, but also environmental science.

• Applied Chemistry for Engineering
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• v.23 no.2
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• pp.148-152
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• 2012

Anatase and anatase/rutile $TiO_2$ samples were prepared at $HNO_3$/TTIP molar ratio of 0.1, 0.5, 1.0, and 1.5 to study the effects of the physical properties of $TiO_2$ on photocatalytic decomposition of methylene blue. The physical properties of the samples were measured with XRD, SEM, TEM, BET, FT-IR, and UV-vis spectroscopy. Anatase phase was observed at $HNO_3$/TTIP of 0.1 and anatase/rutile phases were observed at $HNO_3$/TTIP of 0.5~1.5. Rutile crystal phase, mesopore size between $TiO_2$ nanoparticles, and surface OH group on $TiO_2$ sample were gradually increased with increasing the molar ratio of $HNO_3$/TTIP and the residual methylene blue concentration before UV irradiation decreased from 78.0 to 53.3%. After UV irradiation, the residual methylene blue concentrations of the samples prepared at $HNO_3$/TTIP of 0.1, 0.5, 1.0, and 1.5 were 20, 14, 11, and 23%, respectively, and the sample prepared at $HNO_3$/TTIP of 1.0 showed the best photocatalytic ability.

• Applied Chemistry for Engineering
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• v.18 no.2
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• pp.148-154
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• 2007

This study was performed to evaluate the application of $TiO_2$ on the photocatalytic treatment of swine wastewater. $TiO_2$ sol was prepared by hydrothermal method with the agent ratio($(C_2H_5)_2NH_2\;mol/Ti(OC_3H_7)_4\;mol)=1$ and R ratio ($H_2O\;mol/Ti(OC_3H_7)_4\;mol)=42$. The effect of parameter on the removal efficiency of swine wastewater in a batch type immobilized photocatalyst system such as initial pH, intensity of UV, dosage of $TiO_2$, air flow rate, and concentration of $H_2O_2$ was examined. Wastewater was effectively eliminated in the presence of both UV light illumination and $TiO_2$. Photocatalytic activity was higher in acidic condition compared to neutral and alkaline conditions. In addition, photocatalytic activity increased with increasing UV light intensity, dosage of $TiO_2$, the flow rate of air and the amount of $H_2O_2$ added as an oxidant, but the excess amount of $H_2O_2$ dosage decreased the removal efficiency.