• 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.

• Transactions of the Korean hydrogen and new energy society
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• v.9 no.1
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• pp.8-15
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• 1998

The catalytic hydrogenation of carbon dioxide has been studied for the fixation of carbon dioxide to mitigate global warming problems, but it needed hydrogen, which the price is still high. Recently, the electrochemical reduction of carbon dioxide has been drawn attractions because carbon dioxide could be converted to the valuable chemicals such as methane, ethane and alcohols electrochemically in the electrolyte solution using a catalytic electrode. This system is simple because the water electrolysis and hydrogenation take place at the same time using the surplus electricity at midnight. In this work, a continuous electrochemical reduction system was fabricated, which was composed of the reduction electrode (copper or perovskite type, $2{\times}2cm^2$), reference electrode(platinum, $2{\times}6cm^2$), standard electrode(Ag/AgCl), and potassium bicarbonate electrolyte solution saturated with carbon dioxide. The quality and quantity of the products and reduction current were analyzed, according to the electrolyte concentration and electrode type.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.173.1-173.1
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• 2016

전이금속 디칼코게나이드는 서로 다른 전이 금속원소와 칼코겐 원소의 결합으로 이루어진 층상 구조의 물질로서, 그래핀과 비슷한 2D 결정성 구조를 지니면서도, 그래핀과는 달리 밴드갭을 가지는 반도체적 성질 때문에 최근 많은 연구가 진행되고 있다. 특히 $WS_2$는 촉매, 전자, 광전자, 센서와 같은 반도체등 다양한 소자에 적용된다. $WS_2$ 합성 방법에는 기계적 박리법, 화학기상증착법, 용액법 등이 있다. 기계적 박리법은 방법이 간단하나 수율이 낮고 균일하게 얻어지지 않으며, 화학기상증착법은 고가의 고온공정이라는 한계점을 가지고 있다. 반면에 용액법은 제조공정이 쉬우며, 저가 대량생산이 가능하다는 이점이 있다. 더욱이 본래 용액법에서는 $WS_2$를 합성하기 위해 $WO_3$를 추가적으로 합성 후 진행하였지만, 쉽게 제조 가능한 $WO_3$ colloidal 용액을 이용하면 sulfurization을 진행하여 $WS_2$를 합성할 수 있다. colloidal 용액을 이용한 합성법은 입자크기 조절이 가능하기 때문에 균일한 나노입자를 uniform 하게 형성할 수 있는 장점이 있다. 본 연구에서는 $WO_3$ colloidal 용액을 spin coating 과 sulfurzation 공정을 거쳐 2D triangle $WS_2$의 합성 및 특성을 분석하였다. 2D $WS_2$의 나노결정구조, 입자 형상 및 광학 특성을 주사전자현미경, 라만 분광기, x-ray 회절분석기 등을 통해 확인하였다. 또한, 합성된 $WS_2$를 이용하여 트랜지스터를 제작하여 전기적 특성을 확인하였다.

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.42-46
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• 2008

Even though fuel cell have high efficiency when pure hydrogen from gas tank is used as a fuel source, it is more beneficial to generate hydrogen from city gas (mainly methane) in residential application such as domestic or office environments. Thus hydrogen is generated by reforming process using hydrocarbon. Unfortunately, the reforming process for hydrogen production is accompanied with unavoidable impurities. Impurities such as CO, $CO_2$, $H_2S$, $NH_3$, $CH_4$, and $CH_4$ in hydrogen could cause negative effects on fuel cell performance. Those effects are kinetic losses due to poisoning of the electrode catalysts, ohmic losses due to proton conductivity reduction including membrane and catalyst ionomer layers, and mass transport losses due to degrading catalyst layer structure and hydrophobic property. Hydrogen produced from reformer eventually contains around 73% of $H_2$, 20% or less of $CO_2$, 5.8% of less of $N_2$, or 2% less of $CH_4$, and 10ppm or less of CO. This study is aimed at investigating the effect of carbon dioxide on fuel cell performance. The performance of PEM fuel cell was investigated using current vs. potential experiment, long run(10 hr) test, and electrochemical impedance measurement when the concentrations of carbon dioxide were 10%, 20% and 30%. Also, the concentration of impurity supplied to the fuel cell was verified by gas chromatography(GC).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.1
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• pp.30-35
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• 2024

In order to improve the efficiency of the water splitting system for hydrogen production, the high overvoltage in the electrochemical reaction caused by the catalyst in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) must be reduced. Among them, transition metal-based compounds are attracting attention as catalyst materials that can replace precious metals such as platinum that are currently used. In this study, nickel foam, an inexpensive metal porous material, was used as a support, and Fe-doped β-Ni(OH)₂ microcrystals were synthesized through a hydrothermal synthesis process. In addition, in order to improve OER properties, changes in the shape, crystal structure, and water splitting characteristics of Fe-Mo co-doped β-Ni(OH)₂ microcrystals synthesized by co-doping with Mo were observed. The changes in the shape, crystal structure, and applicability as a catalyst for water splitting were examined.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.369-372
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• 2009

In the present study, the effect of chemical treatment on graphite nanofibers (GNFs) supports with various concentrated nitric acids was investigated for methanol oxidation. To optimize the electrocatalytic activity, PtRu catalysts were deposited on GNF supports by impregnation method. The surface and structural properties of the GNF supports were characterized by X-ray photoelectron spectroscopy (XPS), element analyzer (EA), and X-ray diffraction (XRD). The morphology of the catalysts was observed by means of transmission electron microscopy (TEM). The electrocatalytic activity of PtRu/GNF catalysts was investigated by cyclic voltammetry measurement. As a result, the oxygen functional groups were introduced on the GNF supports and were gradually increased with increasing of concentrated nitric acid, causing the smaller particle size and higher loading level. And the electrocatalytic activity of the catalysts for methanol oxidation was gradually improved. Consequently, it was found that chemical treatments could influence on surface properties of the carbon supports, resulting in enhancing the electrocatalytic activity of the catalysts for DMFCs.

• 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.

• Clean Technology
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• v.17 no.1
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• pp.78-82
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• 2011

For effectively photochemical hydrogen production, P (negative semiconductor) and B (positive semiconductor) ions (0.1, 0.2, 0.5, and 1.0 mol%) incorporated $TiO_2$ (P- and B-$TiO_2$) nanometer sized particles were prepared using a solvothermal method as a photocatalyst. The characteristics of the synthesized P- and B-$TiO_2$ photocatalysts were analyzed by X-ray Diffraction (XRD), Transmission electron microscopy (TEM), W-visible spectroscopy (UV-Vis), and Photoluminescence spectra (PL). The evolution of $H_2$ from methanol/water (1:1) photo-splitting over B-$TiO_2$ photocatalysts was enhanced compared to those over pure $TiO_2$ and P-$TiO_2$ photocatalysts; 0.42 mL of $H_2$ gas was evolved after 10 h when 0.5 g of a 1.0 mol% B-$TiO_2$ catalyst was used.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.202-207
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• 2023

In the case of driving water electrolysis by receiving surplus electricity from solar and wind power generation, operation and stopping must be repeated according to weather fluctuations. When the PEMWE(Polymer Electrolyte Membrane Water Electrolysis) is driven and stopped, the PEM fuel cell is in the same state as the PEM fuel cell due to the residual hydrogen and oxygen, and the high potential of the water electrolysis formed during operation is highly likely to cause degradation of the electrode and membrane even during stopping. In this study, in order to check how much degradation of the electrode and membrane progresses during the repeated driving/shutdown process of PEM water electrolysis, the performance decrease was measured by changing the number of driving/shutdown for 144 hours. Changes in electrode catalyst active area, hydrogen permeability and fluorine emision rate of membranes were analyzed to measure changes in the properties of electrodes and polymer membranes. Overall, the PEMWE performance decreased as the number of stops increased. When stopped 5 times in 144 hours, the IrO_x catalyst activity decreased by more than 30%, and the hydrogen permeability increased by 80%, confirming that both the electrode and the membrane were deteriorated.

• Journal of the Korean Electrochemical Society
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• v.19 no.2
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• pp.39-44
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• 2016

Oxygen reduction reaction in the fuel cell (ORR) plays a dominant role in the overall reaction. In addition, the low compatibility between the membrane and the binder consisted of different materials, greatly reduces the efficiency of the fuel cell performance. In view of these two problems, geometrically modified copolymers with 9.9_Bis (4-hydroxyphenyl) were synthesized via condensation reaction instead of conventional biphenol and were adopted as hydrocarbon ionomer binders. By utilizing these binders, two kinds of MEAs using fluorinated Nafion membrane and hydrocarbon based membrane were manufactured in order to electrochemical performance evaluation. With current-voltage curves, there was no significant difference in the 0.6 V when two types of membrane were applied. Also, tafel slope became considerably lower as compared to the Nafion membrane. Thus, it is determined that the new hydrocarbon binder is expected to contribute the improvement in performance of fuel cells.