• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.93-93
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• 2011

Nanostructures consisting of $TiO_2$ particles as a core and carbon as a shell ($TiO_2$@C) were prepared by heat treatment of $TiO_2$ nanoparticles at high temperature in a methane atmosphere. X-ray diffraction and transmission electron microscopy showed that a carbon shell layer was formed well. These structures were used as supports for platinum nanoparticles and the hybrid particles exhibit improved catalytic activity and stability toward ORR compared to Pt on a carbon black (Vulcan XC-72R). It is likely that enhanced catalytic properties of the Pt on $TiO_2$@C could be due to the stability of the core-shell support in comparison with carbon black support.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2140-2144
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• 2012

A polymer support immobilized acidic ionic liquid was prepared by copolymerization of 3-vinyl-1-(4-sulfonic acid)butylimidazolium hydrogen sulfate with styrene in the presence of benzoyl peroxide and its primary application as a solid acidic heterogeneous catalyst to the synthesis of Hantzsch 1,4-dihydropyridines through a one-pot three-component reaction of aromatic aldehydes, ethyl acetoacetate and ammonium acetate was investigated. The results showed that this heterogeneous catalyst has high catalytic activity and the desired products were obtained in good to high yields. Moreover, the catalyst was found to be reusable and a considerable catalytic activity still could be achieved after third run.

• Korean Chemical Engineering Research
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• v.53 no.2
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• pp.262-268
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• 2015

In this study, two types of catalysts were prepared via conventional metal supporting method and encapsulation of metal nanoparticles in the polyelectrolyte multilayers constructed on support. The resulting catalysts were applied to the direct synthesis of hydrogen peroxide, and the effect of catalyst preparation method on the catalyst life as well as hydrogen peroxide productivity was investigated. The catalytic activity was strongly dependent upon the acid strength of support regardless of the catalyst preparation methods and HBEA (SAR=25) with strong acidity was superior to other supports to promote the reaction. In the case of metal supported catalyst, while hydrogen peroxide productivity was higher than that of polyelectrolyte multilayered counterpart, the reaction performance was sharply decreased during catalyst recycling due to the metal leaching. On the other hand, construction of polyelectrolyte multilayers on support weakened the influence of acid support on the reaction medium and therefore resulted in the decrease of catalytic activity and the increase of hydrogen peroxide decomposition as well. It is noted, however, that the catalytic activity was maintained after 5 recycles, which suggests that the introduction of polyelectrolyte multilayers on the support is very effective to suppress the unfavorable metal leaching phenomenon during a reaction.

• Journal of Environmental Science International
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• v.15 no.3
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• pp.221-227
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• 2006

Oxidative TCE decomposition over $TiO_2$-supported single and complex metal oxide catalysts has been conducted using a continuous flow type fixed-bed reactor system. Different types of commercial $TiO_2$ were used for obtaining the supported catalysts via an incipient wetness technique. Among a variety of titanias and metal oxides used, a DT51D $TiO_2\;and\;CrO_x$ would be the respective promising support and active ingredient for the oxidative TCE decomposition. The $TiO_2-based\;CrO_x$ catalyst gave a significant dependence of the catalytic activity in TCE oxidation reaction on the metal loadings. The use of high $CrO_x$ contents for preparing $CrO_x/TiO_2$ catalysts might produce $Cr_2O_3$ crystallites on the surface of $TiO_2$, thereby decreasing catalytic performance in the oxidative decomposition at low reaction temperatures. Supported $CrO_x$-based bimetallic oxide systems offered a very useful approach to lower the $CrO_x$ amounts without any loss in their catalytic activity for the catalytic TCE oxidation and to minimize the formation of Cl-containing organic products in the course of the catalytic reaction.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.132-132
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• 2013

Colloidal synthesis of nanoparticles with well-controlled size, shape, and composition, together with development of in situ surface science characterization tools, such as ambient pressure X-ray photoelectron spectroscopy (APXPS), has brought new opportunities to unravel the surface structure of working catalysts. Recent studies suggest that surface oxides on transition metal nanoparticles play an important role in determining the catalytic activity of CO oxidation. In this talk, I will outline the recent studies on the influence of surface oxides on Rh, Pt, Ru and Co nanoparticles on the catalytic activity of CO oxidation [1-3]. Transition metal nanoparticle model catalysts were synthesized in the presence of poly(vinyl pyrrolidone) polymer capping agent and deposited onto a flat Si support as two-dimensional arrays using the Langmuir-Blodgett deposition technique. APXPS studies exhibited the reversible formation of surface oxides during oxidizing, reducing, and CO oxidation reaction [4]. General trend is that the smaller nanoparticles exhibit the thicker surface oxides, while the bigger ones have the thin oxide layers. Combined with the nature of surface oxides, this trend leads to the different size dependences of catalytic activity. Such in situ observations of metal nanoparticles are useful in identifying the active state of the catalysts during use and, hence, may allow for rational catalyst designs for practical applications. I will also show that the surface oxide can be engineered by using the simple surface treatment such as UV-ozone techniques, which results in changing the catalytic activity [5]. The results suggest an intriguing way to tune catalytic activity via engineering of the nanoscale surface oxide.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.402-402
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• 2012

Bundles of single-walled carbon nanotube (SWCNTs) were grown using catalytic layer supported by self-assembled monolayers (SAMs). Amine-SAMs were introduced on SiO2/Si substrate (SAMs/Si) there then iron nanoclusters solution was dropped on it through spin-coating (Fe/SAMs/Si). This catalytic template was used to grow CNTs and the synthesized carbon material was confirmed the bundles of dense SWCNTs with incorporation of ca.1% nitrogen. The SAMs has played an active role to support catalytic layer and also acted as a source of N-dope onto SWCNTs in CVD.

• Journal of the Korean Society of Combustion
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• v.10 no.3
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• pp.17-24
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• 2005

A sub-millimeter scale catalytic combustor with a simple plate-shaped combustion chamber was fabricated. A porous ceramics support coated with platinum catalyst was placed in the chamber. The combustor has a gallium arsenide window on the top that is transparent to infrared ray. The temperature distribution in the combustion chamber was measured using infrared thermal imager while hydrogen-air premixture is steadily supplied to the combustor. The area where the catalytic reaction took place broaden for higher flow rate and lower equivalence ratio made activated area in the combustion chamber broaden. The amount of coated platinum catalyst did not affect the reaction. Stop of reaction, which is similar to flame quenching of conventional combustion, was investigated. Large content of heat generation and broad activated area are essential criteria to prevent stop of reaction that has a bad effect on the combustor performance.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.7
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• pp.359-363
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• 2006

Single-walled carbon nanotubes (SWCNTs) with few defects and very small amount of amorphous carbon coating have been synthesized by catalytic decomposition of methane in $H_2$ over well-dispersed metal particles supported on MgO. The yield of SWCNTs was estimated to be 88.5% and the purities of SWCNTs thus obtained were more than 90%. Peak of the radial breathing mode in the Raman spectrum demonstrated that the diameters of synthesized CNTs are in the range 0.4-2.0 nm. Our results also indicated that MgO support materials are useful to a large-scale synthesis of high-quality SWCNTs. Increasing temperature could remarkably increase the yield and also improve the quality of SWCNTs from catalytic decomposition of methane. The morphologies and microstructures of the synthesized carbon materials were characterized by scanning electron microscopy (SEM), Thermogravimetric analysis (TGA), Raman spectroscopy, and X-ray diffraction (XRD).

• 한국연소학회:학술대회논문집
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• 2006.10a
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• pp.235-241
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• 2006

Catalytic combustion is one of the suitable methods for micro power source due to high energy density and no flame quenching. Catalyst loading in the micro structured combustion chamber is one of the most important issues in the development of micro catalytic combustors. In this research, to coat catalyst on the chamber wall, two methods were investigated. First, $Al_2O_3$ was selected as a support of Pt and $Pt/Al_2O_3$ was synthesized through the alumina sol-gel procedure. To improve the coating thickness and adhesion between catalyst and substrate, heat resistant and water solvable organic-inorganic hybrid binder was used. Porous silicon was also investigated as a catalyst support for platinum. Through the parametric studies of current density and etching time, fabrication process of $1{\sim}2{\mu}m$ of diameter and about $25{\mu}m$ depth pores was confirmed. Coated substrates were test in the micro channel combustor which was fabricated by the wet etching and machining of SUS 304. Using $Pt/Al_2O_3$ coated substrate and Pt coated porous silicon substrate, conversion rate of fuel was over 95% for $H_2$/Air premixed gas.

• Journal of the Korean Society of Combustion
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• v.11 no.2
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• pp.7-14
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• 2006

Catalytic combustion is one of the suitable methods for micro power source due to high energy density and it can be applied to micro structured chamber without consideration of quenching since it is flameless combustion. Catalyst loading in the micro structured combustion chamber is one of the most important issues in the development of micro catalytic combustors. In this research, to coat catalyst on the chamber wall, two methods were investigated. First, $Al_2O_3$ was selected as a support of Pt and $Pt/Al_2O_3$ was synthesized through the alumina sol-gel procedure. To improve the coating thickness and adhesion between catalyst and substrate, heat resistant and water solvable organic-inorganic hybrid binder was used. Porous silicon was also investigated as a catalyst support for platinum. Through the parametric studies of current density and etching time, fabrication process of $1{\sim}2{\mu}m$ of diameter and about $25{\mu}m$ depth pores was confirmed. Coated substrates were test in the micro channel combustor which was fabricated by the wet etching and machining of SUS 304. Using $Pt/Al_2O_3$ coated substrate and Pt coated porous silicon substrate, conversion rate of fuel was over 95 % for $H_2/Air$ premixed gas.