• Journal of Electrochemical Science and Technology
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• v.14 no.2
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• pp.131-138
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• 2023

The carbon felt is usually hired as electrodes for vanadium redox flow battery (VRFB). In the study, surface modification of carbon felt under CO₂ atmosphere with variables of operating various temperature ranges between 700℃ and 900℃. The qualitative and quantitative analysis were carried out such as scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) to observe degree of surface modification. Result of XPS analysis confirmed increase of carbon and oxidation functional group on the surface with increase of temperature. SEM image was discovered similar phenomena. Electrochemical characteristics such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed the improved electrode performance with increase of temperature. However, the electrochemical performance under treatments temperature of 900℃ was less than that of under treatment temperature of 850℃ due to weight loss at the treatment temperature of 900℃. From the CV and EIS results, the best electrochemical characteristics was at the temperature of 850℃. That of at the temperature of 900℃ was decreased due to weight loss. The energy efficiencies (EE) obtained from full cell test were 69.37, 80.76, 82.45, and 75.47%, at the temperature of 700, 800, 850, and 900℃, respectively.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.142-147
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• 2021

Hydrogen peroxide is a radiolysis product of water formed under gamma-irradiation; therefore, its reliable detection is crucial in the nuclear industry for spent fuel management and coolant chemistry. This study proposes an electrochemical sensor for hydrogen peroxide detection. Cysteamine (CYST), gold nanoparticles (GNPs), and horseradish peroxidase (HRP) were used in the modification of a gold electrode for fabricating Au/CYST/GNP/HRP sensor. Each modification step of the electrode was investigated through electrochemical and physical methods. The sensor exhibited strong sensitivity and stability for the detection and measurement of hydrogen peroxide with a linear range of 1-9 mM. In addition, the Michaelis-Menten kinetic equation was applied to predict the reaction curve, and a quantitative method to define the dynamic range is suggested. The sensor is highly sensitive to H₂O₂ and can be applied as an electrochemical H₂O₂-sensor in the nuclear industry.

• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.955-958
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• 2009

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.7
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• pp.616-621
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• 2009

Reduction of optical losses in crystalline silicon solar cells by surface modification is one of the most important issues of silicon photovoltaics. Porous Si layers on the front surface of textured Si substrates have been investigated with the aim of improving the optical losses of the solar cells, because an anti-reflection coating(ARC) and a surface passivation can be obtained simultaneously in one process. We have demonstrated the feasibility of a very efficient porous Si ARC layer, prepared by a simple, cost effective, electrochemical etching method. Silicon p-type CZ (100) oriented wafers were textured by anisotropic etching in sodium carbonate solution. Then, the porous Si layers were formed by electrochemical etching in HF solutions. After that, the properties of porous Si in terms of morphology, structure and reflectance are summarized. The structure of porous Si layers was investigated with SEM. The formation of a nanoporous Si layer about 100nm thick on the textured silicon wafer result in a reflectance lower than 5% in the wavelength region from 500 to 900nm. Such a surface modification allows improving the Si solar cell characteristics. An efficiency of 13.4% is achieved on a monocrystalline silicon solar cell using the electrochemical technique.

• Journal of the Korea Safety Management & Science
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• v.2 no.4
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• pp.187-195
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• 2000

Electrochemical promotion of the reaction rate was investigated for CO oxidation in a solid electrolyte catalytic reactor where a thin film of Pt was deposited on the yttria stabilized zirconia as an electrode as well as a catalyst. It was shown under open circuit condition that potential was a mixed potential of $O_2$exchange reaction and electrochemical reaction induced by CO. The effect of electrochemical modification on the CO oxidation rate was studied at various overpotentials and $P_{CO}$$P_{O2}$.

• Journal of Surface Science and Engineering
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• v.41 no.5
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• pp.194-198
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• 2008

Several methods for improving dispersion of carbon nanotubes (CNTs) have been investigated. CNTs modified by acids and hydrogen peroxide ($H_2O_2$) showed improved dispersion. From SEM micrographs and photos of dispersion, CNTs modified with nitric acid and $H_2O_2$, showed no agglomeration in solution even standing for 4 months, which means successfully improved dispersion property. TEM micrographs of surface modified single CNT treated with 69% $HNO_3$ in boiling acid solution as the optimum method were obtained. For confirmation of CNTs' application to EDLC electrode materials, characteristics of EDLC have been analyzed by cyclic voltammetry curve, specific capacitance of unit cell, electrode discharge curves and AC impedance curve. From the results, it could be confirmed that electrochemical properties of CNTs were enhanced after surface modification with 69% $HNO_3$ acid treatment.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1305-1311
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• 2014

The nickel oxide, the most widely used cathode material for the molten carbonate fuel cell (MCFC), has several disadvantages including NiO dissolution, poor mechanical strength, and corrosion phenomena during MCFC operation. The surface modification of NiO with lanthanum maintains the advantages, such as performance and stability, and suppresses the disadvantages of NiO cathode because the modification results in the formation of $LaNiO_3$ phase which has high conductivity, stability, and catalytic activity. As a result, La-modified NiO cathode shows low NiO dissolution, high degree of lithiation, and mechanical strength, and high cell performance and catalytic activity in comparison with the pristine NiO. These enhanced physico-chemical and electrochemical properties and the durability in marine environment allow MCFC to marine application as a auxiliary propulsion system.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.499-513
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• 2020

Among the many studies of carbon-based nanomaterials, carbon-based dots (CDs) have attracted considerable interest owing to their large surface area, intrinsic low-toxicity, excellent biocompatibility, high solubility, and low-cost with environmentally friendly routes, as well as their ability for modification with other nanomaterials. CDs have several applications in biosensing, photocatalysis, bioimaging, and nanomedicine. In addition, the fascinating electrochemical properties of CDs, including high active surface area, excellent electrical conductivity, electrocatalytic activity, high porosity, and adsorption capability, make them potential candidates for electrochemical sensing materials. This paper reviews the recent developments and synthesis of CDs and their composites for the proposed electrochemical sensing platforms. The electrochemical principles and future perspective and challenges of electrochemical biosensors are also discussed based on CDs-nanocomposites.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.295-298
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• 2007

Reduction of optical losses in crystalline silicon solar cells by surface modification is one of the most important issues of silicon photovoltaics. Porous Si layers on the front surface of textured Si substrates have been investigated with the aim of improving the optical losses of the solar cells, because an anti-reflection coating(ARC) and a surface passivation can be obtained simultaneously in one process. We have demonstrated the feasibility of a very efficient porous Si ARC layer, prepared by a simple, cost effective, electrochemical etching method. Silicon p-type CZ (100) oriented wafers were textured by anisotropic etching in sodium carbonate solution. Then, the porous Si layers were formed by electrochemical etching in HF solutions. After that, the properties of porous Si in terms of morphology, structure and reflectance are summarized. The structure of porous Si layers was investigated with SEM. The formation of a nanoporous Si layer about 100nm thick on the textured silicon wafer result in a reflectance lower than 5% in the wavelength region from 500 to 900nm. Such a surface modification allows improving the Si solar cell characteristics. An efficiency of 13.4% is achieved on a monocrystalline silicon solar cell using the electrochemical technique.

• Bulletin of the Korean Chemical Society
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• v.29 no.9
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• pp.1737-1741
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• 2008

The electrochemical and thermal stability of $LiNi_{0.8}Co_{0.16}Al_{0.04}O_2$ were studied before and after $Co_3(PO_4)_2$ coating. Different to conventional coating material such as $ZrO_2$ or AlPO4, the coating layer was not detected clearly by TEM analysis, indicating that the $Co_3(PO_4)_2$ nanoparticles effectively reacted with surface impurities such as $Li_2CO_3$. The coated sample showed similar capacity at a low C rate condition. However, the rate capability was significantly improved by the coating effect. It is associated with a decrease of impedance after coating because impedance can act as a major barrier for overall cell performances in high C rate cycling. In the DSC profile of the charged sample, exothermic peaks were shifted to high temperatures and heat generation was reduced after coating, indicating the thermal reaction between electrode and electrolyte was sucessfully suppressed by $Co_3(PO_4)_2$ nanoparticle coating.