• International Journal of Highway Engineering
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• v.19 no.1
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• pp.53-62
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• 2017

PURPOSES : This research was a fundamental study on the application of an integral $TiO_2$ solution to asphalt concrete pavement. The integral $TiO_2$ solution was produced in pilot production equipment; application of the integral $TiO_2$ solution to asphalt pavement was conducted to examine the pollution-reducing capability of photocatalytic compounds such as $TiO_2$. The photocatalytic $TiO_2$ reacted with air pollutants, converting them into small amounts of relatively benign molecules. METHODS : In this study, laboratory experiments were conducted using five various testing methods. Tensile strength ratio (TSR) and British pendulum test (BPT) were conducted in order to evaluate the properties of asphalt pavement subsequent to the integral $TiO_2$ solution coating. In addition, methylene blue testing, a measurement of nitrate on the coated pavement, and nitrogen oxide (NOx) reduction testing were conducted in order to evaluate photocatalytic reaction. Lastly, a UV-A lamp was used as a light source for photocatalytic reactions. RESULTS : Test results indicated no change in the properties of asphalt pavement following the integral $TiO_2$ solution coating. In order to evaluate the performance of asphalt pavement as a function of $TiO_2$, the moisture susceptibility and skid resistance were investigated. The moisture susceptibility and skid resistance satisfied there quirements related to pavement quality and safety specification. Furthermore, the effects of reduction of air pollution were significantly improved as determined via the methylene blue test and NOx reduction test. The $TiO_2$-paved asphalt specimen exhibited approximately 43% reduction of NOx. CONCLUSIONS : This study has suggested that applying $TiO_2$ rarely impacts asphalt pavement performance measures such as moisture susceptibility and skid resistance, and that its application may be a better means of reducing air pollution. Further studies, such as proper $TiO_2$ dosage rates and compatibility with various pavement types, are required to broaden and generalize its application.

• Korean Journal of Materials Research
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• v.22 no.10
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• pp.504-507
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• 2012

Synthesis of RGO (reduced graphene oxide)-CdS composite material was performed through CBD (chemical bath deposition) method in which graphene oxide served as the support and Cadmium Sulfate Hydrate as the starting material. Graphene-based semiconductor photocatalysts have attracted extensive attention due to their usefulness for environmental and energy applications. The band gap (2.4 eV) of CdS corresponds well with the spectrum of sunlight because the crystalline phase, size, morphology, specic surface area and defects, etc., of CdS can affect its photocatalytic activity. The specific surface structure (morphology) of the photocatalyst can be effective for the suppression of recombination between photogenerated electrons and holes. Graphene (GN) has unique properties such as a high value of Young's modulus, large theoretical specific surface area, excellent thermal conductivity, high mobility of charge carriers, and good optical transmittance. These excellent properties make GN an ideal building block in nanocomposites. It can act as an excellent electron-acceptor/transport material. Therefore, the morphology, structural characterization and crystal structure were observed using various analytical tools, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. From this analysis, it is shown that CdS particles were well dispersed uniformly in the RGO sheet. Furthermore, the photocatalytic property of the resulting RGO-CdS composite is also discussed in relation to environmental applications such as the photocatalytic degradation of pollutants. It was found that the prepared RGO-CdS nanocomposites exhibited enhanced photocatalytic activity as compared with that of CdS nanoparticles. Therefore, better efficiency of photodegradation was found for water purification applications using RGO-CdS composite.

• Journal of the Korean institute of surface engineering
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• v.54 no.6
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• pp.340-347
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• 2021

Among various metal oxide semiconductors, ZnO has an excellent electrical, optical properties with a wide bandgap of 3.3 eV. It can be applied as a photocatalytic material due to its high absorption rate along with physical and chemical stability to UV light. In addition, it is important to control the morphology of ZnO because the size and shape of the ZnO make difference in physical properties. In this paper, we demonstrate synthesis of size-controlled ZnO tetrapods using an atmospheric pressure plasma system. A micro-sized Zn spherical powder was continuously introduced in the plume of the atmospheric plasma jet ignited with mixture of oxygen and nitrogen. The effect of plasma power and collection sites on ZnO nanostructure was investigated. After the plasma discharge for 10 min, the produced materials deposited inside the 60-cm-long quartz tube were obtained with respect to the distance from the plume. According to the SEM analysis, all the synthesized nanoparticles were found to be ZnO tetrapods ranging from 100 to 600-nm-diameter depending on both applied power and collection site. The photocatalytic efficiency was evaluated by color change of methylene blue solution using UV-Vis spectroscopy. The photocatalytic activity increased with the increase of (101) and (100) plane in ZnO tetrapods, which is caused by enhanced chemical effects of plasma process.

• Journal of the Korean institute of surface engineering
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• v.56 no.2
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• pp.137-146
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• 2023

Nanosized TiO₂ has been widely investigated in photoelectrochemical or photocatalytic applications due to their intrinsic properties such as suitable band position, high photocorrosion resistance, and surface area. In this study, to achieve the high efficiency in photoelectrochemical and photocatalytic performance, TiO₂ nanotubular structures were formed by anodization at various temperatures and times. The morphological and crystal structure of the anodized TiO₂ nanotubes (NTs) were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The photoelectrochemical (PEC) properties and incident photon-to-current conversion efficiency (IPCE) of the TiO₂ NTs were studied with different lengths and morphologies. From the detailed investigations, the optimum thickness of TiO₂ nanotubes was 3 ㎛. Moreover, we found that the optimum photocatalytic pollutant removal efficiency of TiO₂ nanotubes for photodegradation of Rhodamine B (RhB) under simulated solar light was 5.34 ㎛ of tube length.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.195-202
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• 2013

$TiO_2$ powders were prepared from titanium (IV) sulfate ($Ti(SO_4)_2$) solution using ammonia solution at low reaction temperature ($80{\sim}100^{\circ}C$) and atmospheric pressure by hydrothermal precipitation method without calcination. The effect of reaction conditions, such as reaction temperature, initial concentration of titanium (IV) sulfate ($Ti(SO_4)_2$) solution, pH of mixture solution and the physical properties of the prepared $TiO_2$, such as crystallite structure, crystallite size were investigated. The photocatalytic activity of prepared $TiO_2$ was tested by the photolysis of brilliant blue FCF (BB-FCF) under the UV and the analysis of UV-VIS diffuse reflectance spectroscopy (DRS). The physical properties of prepared $TiO_2$ were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence spectrometer (PL), particle size distribution measurements. The crystallite size and crystallinity of prepared $TiO_2$ increased with increasing titanium (IV) sulfate ($Ti(SO_4)_2$) concentration, but photocatalytic activity decreased. The crystallite size decreased with increasing pH of mixture solution, but photocatalytic activity increased. The crystallinity and photocatalytic activity increased with increasing reaction temperature. The results showed that anatase type $TiO_2$ could be prepared by hydrothermal precipitation method using titanium (IV) sulfate ($Ti(SO_4)_2$) solution and ammonia solution at low reaction temperature and atmospheric pressure without calcination.

• Journal of Environmental Science International
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• v.19 no.5
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• pp.577-584
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• 2010

The generation of $TiO_2$ nanoparticles by a thermal decomposition of titanium tetraisopropoxide (TTIP) was carried out experimentally using a tubular electric furnace at various synthesis temperatures (700, 900, 1100 and $1300^{\circ}C$) and precursor heating temperatures (80, 95 and $110^{\circ}C$). Effects of degree of crystallinity, surface area and anatase mass fraction of those $TiO_2$ nanoparticles on photocatalytic properties such as decomposition of methylene blue was investigated. Results show that the primary particle diameter obtained from thermal decomposition of TTIP was considerably smaller than the commercial photocatalyst (Degussa, P25). Also, those specific surface areas were more than 134.4 $m^2$/g. Resultant $TiO_2$ nanoparticles showed improved photocatalytic activity compared with Deggusa P25. This is contributed to the higher degree of crystallinity, surface area and anatase mass fraction of $TiO_2$ nanoparticles compared with P25.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.441-447
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• 2014

$AgI/AgCl/H_2WO_4$ double heterojunctions photocatalyst was prepared via deposition-precipitation followed by ion exchange method. The structure, crystallinity, morphology, chemical content and other physical-chemical properties of the samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectra (EDX), UV-vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL). The photocatalytic activity of the $AgI/AgCl/H_2WO_4$ was evaluated by degrading methyl orange (MO) under visible light irradiation (${\lambda}$ > 400 nm). The double heterojunctions photocatalyst displayed more efficient photocatalytic activity than pure AgI, AgCl, $H_2WO_4$ and AgCl/$H_2WO_4$. Based on the reactive species and energy band structure, the enhanced photocatalytic activity mechanism of $AgI/AgCl/H_2WO_4$ was discussed in detail. The improved photocatalytic performance of $AgI/AgCl/H_2WO_4$ double heterojunctions could be ascribed to the enhanced interfacial charge transfer and the inhibited recombination of electron-hole pairs, which was in close relation with the $AgI/AgCl/H_2WO_4$ heterojunctions formed between AgI, AgCl and $H_2WO_4$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.6
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• pp.1302-1307
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• 2006

This study describes the preparation of high-performance photocatalyst and its environmental applications. We prepared visible-light response nano-particle photocatalyst exhibiting the similar photocatalytic activity with $TiO_2$, dispersed $TiO_2$ on $SiO_2$ with an active rutile type titanium oxide prepared at low temperature. The binder and stable photocatalytic $TiO_2$ sol for photocatalytic system were also prepared. Such products were evaluated by UV/Vis spectrometer, X-ray diffraction analysis, SEM, measurement of photocatalytic activities and surface area, mechanical properties of $TiO_2$-coated surfaces. The results obtained can be applied in efficient photocatalytic systems using POF and metal plate for the purification of air.

• Korean Journal of Materials Research
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• v.22 no.7
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• pp.352-357
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• 2012

$SnO_2$-mixed and Sn-doped $TiO_2$ nanoparticles were synthesized via a hydrothermal process. $SnO_2$-mixed $TiO_2$ nanoparticles prepared in a neutral condition consisted of anatase $TiO_2$ nanoparticles(diamond shape, ~25 nm) and cassiterite $SnO_2$ nanoparticles(spherical shape, ~10 nm). On the other hand, Sn-doped $TiO_2$ nanoparticles obtained under a high acidic condition showed a crystalline phase corresponding to rutile $TiO_2$. As the Sn content increased, the particle shape changed from rod-like(d~40 nm, 1~200 nm) to spherical(18 nm) with a decrease in the particle size. The peak shift in the XRD results and a change of the c-axis lattice parameter with the Sn content demonstrate that the $TiO_2$ in the rutile phase was doped with Sn. The photocatalytic activity of the $SnO_2$-mixed $TiO_2$ nanoparticles dramatically increased and then decreased when the $SnO_2$ content exceeded 4%. The increased photocatalytic activity is mainly attributed to the improved charge separation of the $TiO_2$ nanoparticles with the $SnO_2$. In the case of Sn-doped $TiO_2$ nanoparticles, the photocatalytic activity increased slightly with the Sn content due most likely to the larger energy bandgap caused by Sn-doping and the decrease in the particle size. The $SnO_2$-mixed $TiO_2$ nanoparticles generally exhibited higher photocatalytic activity than the Sn-doped $TiO_2$ nanoparticles. This was caused by the phase difference of $TiO_2$.

• Journal of Electrochemical Science and Technology
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• v.7 no.1
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• pp.1-12
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• 2016

The production of oxygen and hydrogen from solar water splitting has been considered to be an ultimate solution for energy and environmental issues, and over the past few years, nano-sized semiconducting metal oxides alone and with graphene have been shown to have great promise for use in photocatalytic water splitting. It is challenging to find ideal materials for photoelectrochemical water splitting, and these have limited commercial applicability due to critical factors, including their physico-chemical properties, the rate of charge-carrier recombination and limited light absorption. This review article discusses these main features, and recent research progress and major factors affect the performance of the water splitting reaction. The mechanism behind these interactions in transition metal oxides and graphene based nano-structured semiconductors upon illumination has been discussed in detail, and such characteristics are relevant to the design of materials with a superior photocatalytic response towards UV and visible light.