• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.570-570
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• 2012

그래핀(graphene)은 육각형의 탄소원자 한층으로 이루어진 이차원 구조체로써 우수한 물리적, 전기적 특성으로 인해 다양한 분야에서 응요을 위한 연구가 활발히 진행되고 있다. 특히, 그래핀과 금속 나노입자의 복합구조는 수소 저장체, 가스센서, 연료전지, 화학 촉매등의 다양한 분야에서 응용이 가능하다. 현재까지 그래핀/금속나노입자 복합구조의 제작 방법에는 열증발(thermal evaporation), 전기도금법(electrodeposition), 표면 기능화(surface functionalization)를 이용한 방법이 보고되었다. 하지만 이러한 방법은 긴 공정시간이 요구되며, 나노입자의 크기 분포가 넓다는 단점을 지닌다. 본 연구에서는 화학기상증착법을 통해 합성된 그래핀이 전사된 SiO2 (300nm)/Si 기판에 염화기가 포함된 백금 화합물 분산용액을 스핀코팅(spin-coating)하고 MeV 전자빔을 조사하여 Pt/grapheme 복합구조를 형성하였다. 이 방법은 균일한 크기 분포의 나노입자의 형성이 가능하며, 간단하고, 대면적 공정이 가능하며, 다른 방법에 비해 그래핀의 결함형성이 적다는 장점을 지닌다. Pt/grapheme 의 기하학적 구조를 주사전자현미경(scanning electron microscopy)와 투과전자현미경(transimission)을 통해 분석하였고, Pt와 graphene의 일함수(workfunction)의 차이에 의해 야기되는 전하이동에 의한 도핑(doping)현상을 라만 분광기(Raman spectroscopy)와 X-선 광전자 분광기(X-ray photoelectron spectroscopy)를 통해 분석하였다.

• Journal of Energy Engineering
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• v.1 no.1
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• pp.58-65
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• 1992

Pt loaded porous carbon Pt/C electrode was prepared by hot pressing process to enhance the electrode performance in PAFC (phosphoric acid fuel cell). By changing the hot pressing conditions and PTFE contents, Pt/C electrodes were prepared and the electrochemical characteristics of oxygen reduction and unit-cell performance were evaluated. The optimum condition of hot press to make electrode is 360$^{\circ}C$ and 10 kg/$\textrm{cm}^2$. Maximum performance was obtained at 30 wt% PTFE content in the catalyst layer with 80% utilization of platinum clusters. Unit-cell performance of hot pressed Pt/C electrode was 200 mA/$\textrm{cm}^2$ at 700 ㎷ and stable performance was maintained more than 200 hr.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.34-35
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• 2008

We investigated the effects of Pt nano electrodeposits on the corrosion of carbon substrate in an acidic solution. The electrodes for experiments were prepared by electrodepositing Pt on carbon substrate in a solution of 5 mM $H_2PtCl_6$ and 0.5 M $H_2SO_4$ using pulse deposition technique. In cyclic voltammograms for the carbon electrodes with and without Pt nano electrodeposits, total anodic current including both currents from oxygen evolution reaction and carbon corrosion increased abruptly above a critical potential. In addition, the critical potential of the carbon electrodes with Pt nano electrodeposits was lower than that of bare carbon electrode. This phenomenon was more prominent at $75^{\circ}C$ than $25^{\circ}C$. In potentiostatic experiments, the current transients and the corresponding power spectral density increased with increasing the applied potential for the electrodes. Furthermore, the current transients for the carbon electrodes with Pt nano electrodeposits were much higher than those for the bare carbon substrate. This indicates that the corrosion of carbon substrate can be highly accelerated by Pt nano electrodeposits.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1520-1521
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• 2007

고분자 전해질 연료전지(PEMFC, polymer electrolyte membrane fuel cell)는 수소이온특성을 갖는 고분자막을 전해질로 사용하는 연료전지로서 무공해 차량의 동력원, 가정용 발전, 우주선용 전원, 군사용 전원 등 매우 다양한 부분에서 사용되어질 것으로 사료된다. 하지만 현재 높은 가격과 짧은 수명 등의 문제로 상용화에 이르지 못하고 있다. 고분자전해질 연료전지의 스택 가격을 부품별로 조사하여 보면 분리판이 전체 스택가격의 60% 정도가 가장 높은 비중을 차지하며 기체 확산층으로 사용되는 탄소재료가 12%,전해질이 10%, 촉매가 8% 정도를 차지한다. 촉매 또한 저가의 비귀금속 촉매를 개발하거나 백금 촉매의 성능을 향상시켜 촉매 사용량을 낮춤으로써 가격을 낮추기 위한 연구가 진행되어지고 있으며 전해질로 사용하는 고분자막도 가격이 매우 높은 Nafion 대신 저가 고분자를 개발하거나, 또는 가능한 얇은 전해질을 사용하기 위한 노력이 이루어지고 있다. 하지만 아직까지는 뚜렷한 진척성과가 없는 것으로 알려져 있다. 그래서 본 연구에서는 고분자 전해질 연료전지의 고분자 Membrane의 특성을 향상시키고 또한 박막의 배양성과 특성에 대해서 고찰해 보고자한다.

• Korean Journal of Materials Research
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• v.25 no.3
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• pp.113-118
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• 2015

To improve the methanol electro-oxidation in direct methanol fuel cells(DMFCs), Pt electrocatalysts embedded on porous carbon nanofibers(CNFs) were synthesized by electrospinning followed by a reduction method. To fabricate the porous CNFs, we prepared three types of porous CNFs using three different amount of a styrene-co-acrylonitrile(SAN) polymer: 0.2 wt%, 0.5 wt%, and 1 wt%, respectively. A SAN polymer, which provides vacant spaces in porous CNFs, was decomposed and burn out during the carbonization. The structure and morphology of the samples were examined using field emission scanning electron microscopy and transmission electron microscopy and their surface area were measured using the Brunauer-Emmett-Teller(BET). The crystallinities and chemical compositions of the samples were examined using X-ray diffraction and X-ray photoelectron spectroscopy. The electrochemical properties on the methanol electro-oxidation were characterized using cyclic voltammetry and chronoamperometry. Pt electrocatalysts embedded on porous CNFs containing 0.5 wt% SAN polymer exhibited the improved methanol oxidation and electrocatalytic stability compared to Pt/conventional CNFs and commercial Pt/C(40 wt% Pt on Vulcan carbon, E-TEK).

• Journal of the Korean Vacuum Society
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• v.10 no.3
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• pp.289-297
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• 2001

Highly-porous $SnO_2$thin films were prepared for recognizing and detecting of the inflammable gases, like butane, propane, LPG, carbon monoxide. To obtain sensing films, Sn, Pt/Sn, Au/Sn, and Pt,Au/Sn films were deposited employing a thermal evaporator for Sn film and a sputter for novel metals of Pt or/and Au. These films were annealed for 2 h at $700^{\circ}C$ to form $SnO_2$-based thin films. The films showed the tetragonal structure and also exhibited many defects and porosity, which could give high sensitivity to thin films. The thin films showed high sensitivity and reproductivity to the tested gases(butane, propane, LPG, and carbon monoxide) to even to low gas concentrations in range of workplace environmental standards. Especially, Pt/$SnO_2$film showed the highest sensitivity to butane, LPG, and carbon monoxide. And pure $SnO_2$ film manifested the highest sensitivity to propane. By using the sensing patterns from the films, we could reliably recognize the kinds and the quantities of the tested inflammable gases within the range of the threshold limit values(TLV) and the lower explosion limit(LEL) through the principal component analysis(PCA).

• Clean Technology
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• v.17 no.2
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• pp.166-174
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• 2011

The xAl-yCe oxide catalysts with different mol ratios of Al/(Al+Ce) were prepared by a co-precipitation method and Pt supported on xAl-yCe oxide catalysts were synthesized by an incipient wetness impregnation method. The catalysts were characterized by X-ray Diffraction (XRD), $N_2$ sorption, and $H_2$/CO-temperature programmed reduction ($H_2$/CO-TPR) to correlate with catalytic activities in co oxidation. Among the catalysts studied here, Pt/1Al-9Ce oxide catalyst showed the highest activity in dry and wet reaction conditions and the catalytic activity showed a typical volcano-shape curve with respect to Al/(Al+Ce) mol ratio. When the presence of 5% water vapor in the feed, the temperature of $T_{50%}$ was shifted ca. $30^{\circ}C$ to lower temperature region than that in dry condition. From CO-TPR, the desorption peak of $CO_2$ on Pt/1Al-9Ce oxide catalyst showed the highest value and well correlated the catalytic performance. It indicates that the Pt/1Al-9Ce oxide catalyst has a large amount of active sites which can be adsorbed by co and easy to supplies the needed oxygen. In addition, the amount of pentacoordinated $Al^{3+}$ sites obtained through $^{27}Al$ NMR analysis is well correlated the catalytic performance.

• Clean Technology
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• v.13 no.1 s.36
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• pp.54-63
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• 2007

Even traces of CO in the hydrogen-rich feed gas to proton exchange membrane fuel cells (PEMFC) poison the platinum anode electrode and dramatically decrease the power output. In this work, a variety of catalytic materials consisting of $Cu/Ce_xZr_{1-x}O_2$, (x = 0.0-1.0) were synthesised, characterized and tested for CO oxidation and preferential oxidation of CO (PROX). These catalysts prepared by hydrothermal and deposition-precipitation methods. The catalysts were characterized by XRD, XRF, SEM, BET, $N_2O$ titration and oxygen storage capacity (OSC) measurement. The effects of composition of the support and degree of excess oxygen were investigated fur activity and $CO_2$ selectivity with different temperatures. The composition of the support markedly influenced the PROX activity. Among the various $Cu/Ce_xZr_{1-x}O_2$ catalysts having different composition, $Cu/Ce_{0.9}Zr_{0.1}O_2$ and $Cu/Ce_{0.7}Zr_{0.3}O_2$ showed the highest activities (>99%) and selectivities (ca.50%) in the temperature range of $150{\sim}160^{\circ}C$. It was found that by using of $Ce_xZr_{1-x}O_2$ mixed oxide support which possesses a high oxygen storage capacity, oxidation-reduction activity of Cu-based catalyst was improved, which resulted in the increase of catalytic activity and selectivity of CO oxidation in excess $H_2$ environments.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.11
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• pp.1977-1983
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• 2000

SCR(selective catalytic reduction) pilot plant for reduction of the nitrogen oxides using diesel oil as a reductant was installed at the NG(natural gas) fired combined cycle and the activity of Pt(0.3%)/Zeolite catalyst was studied in real flue gas condition according to the amount of reductant. reaction temperature and space velocity. NOx conversion gradually increased with increasing the diesel oil concentration up to C/N ratio 5.5(C/N ratio: the ratio of the number of carbon atom to the number of NOx molecules included in the flue gas). Increasing the reaction temperature. NOx conversion increased and reached a maximum conversion of 50% at $190^{\circ}C$. NOx conversion did not changed with increasing the space velocity up to 18,500/hr and then gradually decreased. These results reveal the potential for diesel oil as a reductant for de-NOx SCR process.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.4
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• pp.142-149
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• 2012

The reduction characteristics of $NO_2$ to NO are experimentally studied over a platinum-based catalyst, especially at lower temperatures below about $200^{\circ}C$. In the present work, two types of steady-state experiments, engine bench and synthetic gas bench tests, are carried out in sequence. Steady-state engine bench tests with the DOC mounted on a light duty 4-cylinder 2.0 liter turbocharged diesel engine are performed and prove that CO plays a major role in $NO_2$ abatement at temperatures below the light-off temperature of CO oxidation, about $200^{\circ}C$. Synthetic gas bench tests are then performed using synthetic gas mixtures with CO, $C_3H_6$, NO, $NO_2$, $O_2$, $H_2O$ and $N_2$ in the $140{\sim}450^{\circ}C$ T-range and show that both CO and $C_3H_6$ are capable of reducing $NO_2$. It is noted that the reaction rate of $NO_2$ with $C_3H_6$ is much higher than that with CO. At temperatures below about $200^{\circ}C$, the reduction of $NO_2$ to NO is promoted with increasing CO concentration and $NO_2$/$NO_X$ ratio and with decreasing $O_2$ concentration, as well as with the presence of $H_2O$.