• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.9.1-9.1
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• 2011

나노입자는 벌크에 비해 월등히 큰 비표면적(surface-to-volume ratio)과 작은 사이즈에서 오는 양자효과로 인해 촉매나 나노 전자 소자 등 여러 분야에서 응용되고 있다. 특히 백금 나노입자는 수소나 메탄올의 산화, 산소환원 반응의 독보적인 촉매로서 연료전지의 산화극과 환원극의 촉매로 널리 활용되고 있다. 본 연구에서는 높은 가격의 백금의 사용량을 줄일 수 있는 합금 나노입자 촉매에 대한 연구의 일환으로 Pd, Au, Cu, Ag 등의 원소를 활용한 합금 나노입자에 대한 구조 및 열역학적 안정성에 대한 연구를 수행하였다. 다양한 합금에 대한 원자간 포텐셜을 개발하였고, 이를 기반으로 몬테카를로 및 분자동력학 시뮬레이션을 수행하여 Pd-Pt, Cu-Pt, Ag-Pt, Au-Pt 이원계 합금 나노입자의 다양한 원자 구조 및 형상에 따른 결합에너지와 열역학적 특성에 대하여 분석하였다.

• Clean Technology
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• v.27 no.1
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• pp.9-16
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• 2021

Since the active matrix organic light-emitting diode (AMOLED) encapsulation process is very vulnerable to moisture and oxygen, high-purity nitrogen with minimal moisture and oxygen must be used. In this study, a copper-based catalyst used to remove oxygen from nitrogen in the AMOLED encapsulation process was optimized. Two-component and three-component catalysts composed of CuO, Al2O3, or ZnO were prepared through a co-precipitation method. The prepared catalysts were characterized by using BET, XRD, TPR, and XRF analysis. In order to verify the oxygen removal performance of the catalyst, several catalytic reactions were conducted in a fixed bed reactor, and the corresponding oxygen contents were measured through an oxygen analyzer. In addition, reusability of the catalysts was proven through repetitive regeneration. The properties and oxygen removal capacity of the catalysts prepared with CuO and Al2O3 ratios of 6 : 4, 7 : 3, and 8 : 2 were compared. The number of active sites of the catalyst with a ratio of CuO and Al2O3 of 8 : 2 was the highest among the 2-component catalysts. Moreover, the reducibility of the catalyst with a ratio of CuO and Al2O3 of 8 : 2 was the best as it had the highest CuO dispersion. As a result, the oxygen removal ability of the catalyst with a ratio of CuO and Al2O3 of 8 : 2 was the best among the 2-component catalysts. The best oxygen removal capacity was obtained when 2wt% of ZnO was added to the sub-optimized catalyst (i.e., CuO : Al2O3 = 8 : 2) probably due to its outstanding reducibility. Furthermore, the optimized catalyst kept its performance during a couple of regeneration tests.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.396-400
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• 1997

중수형 발전소에서 삼중수소 제거나 중수분리와 관련된 수소동위원소 교환반응에 이용되는 백금담지 고분자촉매제조시 환원과정 이전의 열처리 조건이 백금분산도에 미치는 영향을 관찰하였다. 고분자 담체(SDBC)에 함침법을 이용하여 백금을 담지시켰으며, 8$0^{\circ}C$의 공기중에서 그리고 15$0^{\circ}C$의 산소흐름하에서 열처리하여 제조한 Pt/SDBC촉매의 열적 안정성을 TGA와 BET 실험결과로부터 확인할 수 있었다. 백금담지량이 커지면 백금분산도가 감소하였으며, 가능한 한 고온의 산소로 열처리하면 고분자촉매의 백금분산도가 향상됨을 수소흡착 실험을 통하여 입증하였다.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.537-541
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• 2010

Pt-Sn with various ratios was supported on carbon black after pretreatment in an acidic solution by a reduction method. The Pt/Sn ratio was controlled by varying the concentration of each component in the solution, and the influence of the composition on the electrocatalytic activities was investigated. The crystallinity of the synthesized materials was investigated by XRD (X-ray Diffraction), and the oxidation states of both the platinum and tin were determined by XPS (X-ray Photoelectron Spectroscopy). SEM (Scanning Electron Microscopy)-EDS (Energy Dispersive Spectroscopy) was utilized to examine the morphology and composition of the synthesized electrode, and the particle size of the Pt-Sn was analyzed by TEM (Transmission Electron Microscopy). The electrocatalytic activity for oxygen reduction was evaluated in a 0.5 M $H_2SO_4$ solution using a rotating disk electrode system. The activity and stability were found to be strongly dependent on the electrode composition (Pt/Sn ratio). The catalytic activity and stability for methanol oxidation were also measured using cyclic voltammetry (CV) in a mixture of 0.5 M $H_2SO_4$ and 0.5 M $CH_3OH$ aqueous solution. The addition of proper amount of Sn was found to significantly improve both catalytic activity and stability for methanol oxidation.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.605-609
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• 2011

We study on the oxygen behavior of $V_2O_5/TiO_2$ catalysts in the $NH_3$-selective catalytic reduction (SCR) prepared by the ball milling processing. There are not any changes in crystal structure and surface area of the $TiO_2$ catalyst by ball milling, but the maximal reduction temperature decreased in $H_2$-temperature programmed reduction (TPR) analysis. Experimental observations with various concentrations of oxygen indicate that all catalysts showed a very low NOx conversion rate in the absence of oxygen and the reactivity of ball milled catalyst higher depending on the oxygen. It is occurred because the degree of participation of atmospheric oxygen and lattice oxygen is great than that of the not-milled catalyst.

• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.459-467
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• 2022

Redispersion of Pt-Sn particles in Pt, PtSn catalyst which have been sintered by high temperature hydrogen reduction was investigated using oxygen treatment with various temperatures. The aim of this study was to understand the relationship between the catalytic activity for propane dehydrogenation reaction and the change in the physicochemical properties of the catalyst. X-ray diffraction analysis (XRD), CO pulse chemisorption, and H₂ temperature programmed reduction (H₂-TPR) were performed to investigate the state of active metal and interactions between particles of redispersed catalyst. It was confirmed that the dispersion and particle size of platinum, the crystal phase of the catalyst, and the reduction behavior were changed according to the oxygen treatment. As for the catalytic activity in propane dehydrogeantion, sintered PtSn catalyst treated with oxygen at 500 ℃ showed best activity and recovery of initial activity. It was confirm that catalyst after oxygen treatment at 500 ℃ showed high dispersion of Pt and decreased particle size as the results of CO pulse chemisorption and XRD of catalyst, and thus the redispersion of PtSn particles in sintered catalyst was occurred. Catalytic activity was recovered due to redispersion using oxygen treatment, and the activity recovery of the PtSn catalyst was higher than that of Pt catalyst.

• Applied Chemistry for Engineering
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• v.7 no.5
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• pp.992-998
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• 1996

The $La_{0.8}Ca_{0.2}CoO_3$ prepared by a citrate process was shown to have higher oxygen reduction current density and specific activity than $LaCoO_3$, $La_{0.6}Ca_{0.4}CoO_3$. In the cyclic voltammogram, an oxygen desorption peak of a $La_{0.8}Ca_{0.2}CoO_3$+carbon electrode was larger than that of a only carbon electrode. $La_{0.8}Ca_{0.2}CoO_3$ sintered at $900^{\circ}C$ for 5 hours was shown high oxygen reduction current density because of the particle size distribution and sintering effect.

• Journal of the Korean Chemical Society
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• v.37 no.4
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• pp.462-469
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• 1993

The electrocatalytic reduction of dioxygen is investigated by cyclic voltammetry and chronoamperometry at glassy carbon electrode and carbon microelectrode coated with a variety of cobalt phenylporphyrins. The n value obtained at carbon microelectrode is slightly different from that determined at glassy carbon electrode. Dioxygen reduction catalyzed by the monormeric porphyrin Co(II)-TPP mainly occurs through the $2e^-$ reduction pathway resulting in the formation of hydrogen peroxide, electrocatalytic process carries out $4e^-$ reduction pathway of dioxygen to $H_2O$ at the electrodes coated with bis-cobalt phenylporphyrins. The electrocatalytic reduction of dioxygen is irreversible and diffusion controlled.

• Clean Technology
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• v.21 no.4
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• pp.248-256
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• 2015

MnO₂ was prepared by a hydrothermal process method in the range of 120-200 ℃ and 0.5-5 h, calcined at 300 ℃ after induction of precipitation using KMnO₄ and MnCl₂･4H₂O, and its catalytic activity was compared for CO oxidation. The catalysts were characterized using by X-ray diffraction, N₂-sorption, scanning electron microscopy, and temperature programmed reduction of H₂ or CO. The crystalline structure of pure α-MnO₂ or hybrid α/β-MnO₂ was controlled by the preparation conditions. The pure α-MnO₂ showed better catalytic activity and thermal stability than hybrid α/β-MnO₂. Especially, α-MnO₂ prepared at 150 ℃ for 1 h has the highest specific surface area 214 m² g^-1, reducibility and labile lattice oxygen species analyzed by H₂, CO-TPR, respectively. It also showed the best CO oxidation activity in both conditions of temperature programmed and isothermal reaction. The results came from the physicochemical properties of catalysts like the crystalline structure, specific surface area, reducibility and lattice oxygen species, and which are correlated with catalytic performance.

• Applied Chemistry for Engineering
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• v.18 no.4
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• pp.350-355
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• 2007

The effect of moisture in flue gas on SCR reaction of NMO (Natural Manganese Ore) was studied. The experiments were performed over NMO with NO, $NH_3$ at independent condition or simultaneous condition. $NH_3$ can be oxidized at low temperature by the lattice oxygen in NMO catalyst. The concentration of NO and $NO_2$ by $NH_3$ oxidation with moisture is higher above $300^{\circ}C$ than that without moisture. Moisture would competitively adsorb with NO and $NH_3$ on NMO catalyst. It caused poor NOx conversion to compete against $H_2O$. Besides the NOx conversion efficiency was reduced at below $250^{\circ}C$ because of the dipped $H_2O$ competitively adsorbed $NH_3$. The reactivity of NMO varied with the calcination temperature and the optimum calcination temperature was $400^{\circ}C$ regardless $H_2O$.