• Journal of Electrochemical Science and Technology
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• v.7 no.2
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• pp.146-152
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• 2016

A combined system with PEMFC and reformer is introduced and optimized for the real use of this kind of system in the future. The hydrogen source to operate the PEMFC system is methanol, which needs two parts of methanol reforming reaction and preferential oxidation (PROX) for the hydrogen fuel process in the combined operation PEMFC system. With the optimized methanol steam reforming condition, we tested PROX reactions in various operation temperature from 170 to 270 ℃ to investigate CO concentration data in the reformed gases. Using these different CO concentration, PEMFC performances are achieved at the combined system. Pt/C and Ru promoted Pt/C were catalysts were used for the anode to compare the stability in CO contained gases. The alloy catalyst of PtRu/C shows higher performance and better resistance to CO than the Pt/C at even high CO amount of 200 ppm, indicating a promotion not only to the activity but also to the CO tolerance. Furthermore, in a system point of view, there is a fluctuation in the PEMFC operation due to the unstable fuel supply. Therefore, we also modified the methanol reforming by a scaled up reactor and pressurization to produce steady operation of PEMFC. The optimized system with the methanol reformer and PEMFC shows a stable performance for a long time, which is providing a valuable data for the PEMFC commercialization.

• Journal of the Korean Applied Science and Technology
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• v.33 no.1
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• pp.129-135
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• 2016

CO oxidation was performed with Cu-Mn and Cu-Zn co-precipitated catalysts as differential precipitant, metal ratio and calcination temperature. The effects of differential metal mole ratio and calcination temperature in mixed metal oxide catalyst were investigated with CO oxidation reaction. Physiochemical properties were studied by XRD, $N_2$ sorption and SEM. 2Cu-1Mn with $Na_2CO_3$ catalyst calcined at $270^{\circ}C$ has a large surface area $43m^2/g$ and the best activity for CO oxidation. $Cu_{0.5}Mn_{2.5}O_4$ in XRD peak shows the lower activity than others. The catalytic activity over the catalyst calcined $270^{\circ}C$ displayed the highest conversion, and it was better activity comparing with Pt catalysts CO conversion.

• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.22-27
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• 2018

In this study, the effect of physical properties of $Pt/TiO_2$ on $NH_3$-selective catalytic oxidation (SCO) reaction at $200{\sim}350^{\circ}C$ was investigated. CO-chemisoption and BET analysis were carried out to verify physical properties of $Pt/TiO_2$. By characterizing physical properties of $Pt/TiO_2$ with respect to the Pt loading, the metal dispersion degree decreased as a function of the Pt loading amount. Also, the catalyst having a higher metal dispersion showed an excellent conversion efficiency of $NH_3$ to $N_2$. Since the specific surface area of the support affects the metal dispersion, $Pt/TiO_2$ catalysts were prepared using $TiO_2$ with different physical properties. As a result, it was confirmed that the catalyst having a wide specific surface area exhibited a excellent conversion of $NH_3$ to $N_2$.

• Analytical Science and Technology
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• v.15 no.3
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• pp.263-269
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• 2002

After porous filters were manufactured using cordierite powder whose mean particle size was 200 ${\mu}m$, they were loaded with catalysts such as Pt, Pd, Cu, Co, La, $V_2O_5$ by vacuum impregnation method. And we investigated the activity of catalysts used for catalytic oxidation of VOC by passing toluene through catalyst-loaded filters. The porous filters had the apparent porosity of 62%, the compressive strength of about 10 MPa and the pressure drop of 15 mmHg at the face velocity of 5 cm/sec. The loading of catalyst decreased the porosity of the filters and increased the pressure drop and the compressive strength of them. Among the catalysts, Pt had the highest activity for catalytic oxidation and could remove more than 90% of toluene at 250 $^{\circ}C$. Below 250 $^{\circ}C$, the content of Pt catalyst had an influence on the conversion of toluene but didn't show any influence above 250 $^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.217-217
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• 2011

Recently, demand for thermally stable metal nanoparticles suitable for chemical reactions at high temperatures has increased to the point to require a solution to nanoparticle coalescence. Thermal stability of metal nanoparticles can be achieved by adopting core-shell models and encapsulating supported metal nanoparticles with mesoporous oxides [1,2]. However, to understand the role of metal-support interactions on catalytic activity and for surface analysis of complex structures, we developed a novel catalyst design by coating an ultra-thin layer of titania on Pt supported silica ($SiO_2/Pt@TiO_2$). This structure provides higher metal dispersion (~52% Pt/silica), high thermal stability (~600$^{\circ}C$) and maximization of the interaction between Pt and titania. The high thermal stability of $SiO_2/Pt@TiO_2$ enabled the investigation of CO oxidation studies at high temperatures, including ignition behavior, which is otherwise not possible on bare Pt nanoparticles due to sintering [3]. It was found that this hybrid catalyst exhibited a lower activation energy for CO oxidation because of the metal-support interaction. The concept of an ultra-thin active metal oxide coating on supported nanoparticles opens-up new avenues for synthesis of various hybrid nanocatalysts with combinations of different metals and oxides to investigate important model reactions at high-temperatures and in industrial reactions.

• Journal of Environmental Science International
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• v.26 no.1
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• pp.67-78
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• 2017

Combustion of ethanol (EtOH) at low temperatures has been studied using titania- and silica-supported platinum nanocrystallites with different sizes in a wide range of 1~25 nm, to see if EtOH can be used as a clean, alternative fuel, i.e., one that does not emit sulfur oxides, fine particulates and nitrogen oxides, and if the combustion flue gas can be used for directly heating the interior of greenhouses. The results of $H_2-N_2O$ titration on the supported Pt catalysts with no calcination indicate a metal dispersion of $0.97{\pm}0.1$, corresponding to ca. 1.2 nm, while the calcination of 0.65% $Pt/SiO_2$ at 600 and $900^{\circ}C$ gives the respective sizes of 13.7 and 24.6 nm when using X-ray diffraction technique, as expected. A comparison of EtOH combustion using $Pt/TiO_2$ and $Pt/SiO_2$ catalysts with the same metal content, dispersion and nanoparticle size discloses that the former is better at all temperatures up to $200^{\circ}C$, suggesting that some acid sites can play a role for the combustion. There is a noticeable difference in the combustion characteristics of EtOH at $80{\sim}200^{\circ}C$ between samples of 0.65% $Pt/SiO_2$ consisting of different metal particle sizes; the catalyst with larger platinum nanoparticles shows higher intrinsic activity. Besides the formation of $CO_2$, low-temperature combustion of EtOH can lead to many other pathways that generate undesired byproducts, such as formaldehyde, acetaldehyde, acetic acid, diethyl ether, and ethylene, depending strongly on the catalyst and reaction conditions. A 0.65% $Pt/SiO_2$ catalyst with a Pt crystallite size of 24.6 nm shows stable performances in EtOH combustion at $120^{\circ}C$ even for 12 h, regardless of the space velocity allowed.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.3
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• pp.199-208
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• 2008

HI decomposition was conducted using Pt/C-based catalysts with a fixed-bed reactor in the range of 573 K to 773 K. To examine the change of the characteristic properties of the catalysts, $N_2$ adsorption analyser, a X-ray diffractometer(XRD), and a scanning electron microscopy(SEM) were used before and after the HI decomposition reaction. the effect of Pt loading on HI decomposition was investigated by $CO_2$-TPD. HI conversion of all catalysts increased as decomposition temperature increased. The XRD analysis showed that the sizes of platinum particle became larger and agglomerated into a lump during the reaction. From $CO_2$-TPD, it can be concluded that the cause for the increase in catalytic activity may be attributed to the basic sites of catalyst surface. The results of both b desorption and gasification reaction showed the restriction on the use of Pt/C-based catalyst.

• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.561-566
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• 2012

PtRuW/C catalysts were prepared with the different molar ratios of Pt : Ru : W and their compositions were analyzed by energy dispersive X-ray (EDX). The uniform distribution of particles was observed using transmission electron microscopy (TEM). An average crystalline size of 3.5~5.5 nm was calculated based on x-ray diffraction (XRD) data. The electrochemical properties such as electrochemically active surface areas, current densities, specific activities and poisoning rates, were analyzed via CO stripping, linear sweep voltammetry and chronoamperometry. From the analysis, we observed that ternary alloy catalysts, except $PtRu_2W_2/C$, have higher current densities, specific activities and stabilities than those of commercial binary catalysts. Among all in-house catalysts, Pt5Ru4W/C showed the highest specific activity of $121.05mA{\cdot}m^{-2}$ and the lowest poisoning rate of $0.01%{\cdot}s^{-1}$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2390-2395
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• 2009

In the condition of GHSV=$30000\;hr^{-1}$, $NO_x$ removal yield was higher as mole ratio of $SiO_2/Al_2O_3$ for Fe/ZSM-5 was lower regardless of preparation method such as CVD (chemical vapor deposition) and dry impregnation. In addition to this, Fe/ZSM-5 catalyst showed about 50% $NO_x$ removal yield between $350^{\circ}C$ - $400^{\circ}C$ while CO formed significantly. To remove newly formed CO over Fe/ZSM-5, Co-Pt/ZSM-5 was used in conjunction with Fe/ZSM-5 in the series and this demonstrated over 90% removal yield of both NOx and CO at $250^{\circ}C$ and GHSV=$30000\;hr^{-1}$.

• Particle and aerosol research
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• v.8 no.2
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• pp.69-74
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• 2012

This study describes how successfully a conventional flame aerosol synthesis was used to continuously synthesize Pt-Ru catalysts supported by carbon agglomerates. Nearly spherical catalysts produced in the flame were mainly composed of metallic Pt and Ru with the molar ratio of 1:1 and those sizes were controllable from ~1.5 nm to ~2.0 nm. Nevertheless, only Pt peaks were found from X-ray diffraction experiments, suggesting that amorphous-like Ru was well mixed in the crystalline Pt lattices. It was found from Cyclo-voltamograms and CO stripping experiments that the electrochemical properties of the catalysts are at least comparable to that of a conventional commercial sample.