• Journal of Environmental Science International
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• v.29 no.4
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• pp.383-393
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• 2020

To increase electrolysis performance, the applicability of seawater to the iron-fed electro-Fenton process was considered. Three kinds of graphite electrodes (activated carbon fiber-ACF, carbon felt, graphite) and dimensionally stable anode (DSA) electrode were used to select a cathode having excellent hydrogen peroxide generation and organic decomposition ability. The concentration of hydrogen peroxide produced by ACF was 11.2 mg/L and those of DSA, graphite, and carbon felt cathodes were 12.9 ~ 13.9 mg/L. In consideration of durability, the DSA electrode was selected as the cathode. The optimum current density was found to be 0.11 A/㎠, the optimal Fe²⁺ dose was 10 mg/L, and the optimal ratio of Fe²⁺ dose and hydrogen peroxide was determined to be 1:1. The optimum air supply for hydrogen peroxide production and Rhodamine B (RhB) degradation was determined to be 1 L/min. The electro-Fenton process of adding iron salt to the electrolysis reaction may be shown to be more advantageous for RhB degradation than when using iron electrode to produce hydrogen peroxide and iron ion, or electro-Fenton reaction with DSA electrode after generating iron ions using an iron electrode.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.540-544
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• 2015

A bath for electrodeposition of platinum nanoparitcles on low-cost graphite substrates was developed to attach nanoparticles directly onto a substrate, and electrochemical characteristics of the electrodeposition of platinum nanoparticles were investigated. The reaction mechanism was examined by the analysis of polarization behavior. Cyclic voltammetry measurements revealed that the elecrodeposition of platinum nanoparticles was limited by mass transfer. The chronoamperometric study showed an instantaneous nucleation mechanism during the electrodeposition of platinum nanoparticles on graphite. Because graphite is much cheaper than other carbon-based substrates, the electrodeposition of platinum nanoparticles on the graphite is expected to have useful applications.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.83-90
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• 1998

Stage transformation characteristics of Li, K and Na-graphite deintercalation compounds (GDICs) were studied under consideration of a deintercalation mechanism of the intercalants between carbon layers. Li-graphite intercalation compounds (GICs) synthesized by a controlling temperatures and pressures have been spontaneously decomposed in the atmosphere. By X-ray differaction analysis the $d_{001}$-values of stage 1 and 2 were identified to be 3.71 and 7.06 $\AA$, respectively. After 6 weeks, the deintercalation reaction of the Li-GICs ceased and only residual compounds could be observed. K-GICs were synthesized by the modified two-bulb method resulting in structural stabilities and stage transitions. By X-ray diffraction analysis the very stable K-graphite residue compounds were observed after 10 weeks. Na-GICs with stage 1 and 2 were synthesized using the high temperature and pressure technique. The temperature dependence of a deintercalation reaction and a thermal stability of Na-GICs were discussed. The structure changes of the Na-GDICs depending on heating rates were identified by X-ray diffraction. According to the deintercalation process, the stage transformations could be attributed to irregular deintercalations of the GDICs with disordered stage.

• Journal of Electrochemical Science and Technology
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• v.2 no.2
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• pp.116-123
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• 2011

Herein, a novel preparation method of highly homogeneous carbon-silicon composite materials was presented. In contrast to conventional solvent evaporation method, a milled silicon-graphite or its oxidized material were directly reacted with petroleum-derived pitch precursor. After thermal reaction under high pressure, pitch-graphite-silicon composite was prepared. Carbon-graphite-silicon composite were prepared by an air-oxidization and following carbonization. From energy dispersive spectroscopy, it was observed that small Si particles were highly embedded within carbon, which was confirmed by disappearance of Si peaks in Raman spectra. Furthermore, X-ray diffraction and Raman spectra revealed that carbon crystallinity decreased when the strongly oxidized silicon-graphite was added, which was probably due to oxygen-induced cross-linking. From the anode application in lithium ion batteries, carbon-graphite-silicon composite anode displayed a high capacity ($565\;mAh\;g^{-1}$), a good initial efficiency (68%) and an good cyclability (88% retention at 50 cycles), which were attributed to the high dispersion of Si particles within cabon. In case of the strongly oxidized silicongraphite addtion, a decrease of reversible capacity was observed due to its low crystallinity.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.571-583
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• 1996

The electrochemical behavior on electrographite and graphite foil electrode with porous surface in 0.5 M $K_{2}SO_{4}$ solution with 1 mM $[Fe(CN)_{6}]^{3-}/[Fe(CN)_{6}]^{4-}$ have been characterized by impedance spectroscopy. In cyclic voltammograms, relative high current according to structure of porous surface for graphite materials was represented, and indicated hgih double layer capacitance on graphite foil. The faraday-impedance and the change of impedance spectrum on both graphite materials were not remarkable during polarization by reaction of field transport. Chemical adsorption was represented on electrographite and was depended highly at anodic polarization.

• Journal of the Korean Electrochemical Society
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• v.7 no.1
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• pp.32-37
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• 2004

The charge/discharge capacity of natural graphite anode in lithium secondary batteries was examined as a function of charge/discharge rate. When the natural graphite anode was galvanostatically cycled in the range of 0.0-2.0V $(vs.\;Li/Li^+)$, the charging capacity decreased with an increase in the charging rate, which is caused by an earlier approach to the charging cut-off (0.0 V) before the complete charging that is in turn caused by an ever-increasing overpotential at higher rates. Even if the overpotential of discharging reaction also increased at higher discharge rates, the discharging reaction took place in the range of 0.0-0.3 V that is far below the discharge cut-off (2.0 V). As a result, the discharge capacity was not affected by the discharge rate because all the lithium ions once intercalated are fully discharged even at high current condition. As the overpotential of lithium deposition reaction also increased at high current condition, the charge capacity of natural graphite could be enlarged by lowering the charging cut-off voltage below 0.0 V, There is, however, a limitation for the lowering of cut-off voltage because the resistance for lithium deposition is smaller than that of lithium intercalation into graphite. When the charge cut-off voltage was lowered down to -0.04 V under IC condition, lithium ions were inserted into graphite without lithium deposition such that the discharge capacity could be raised up to $11\%$.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.138.2-138.2
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• 2013

Copper oxide is a multi-functional material being used in various research areas including catalysis, electrochemical materials, oxidizing agents etc. Among these areas, we have synthesized and utilized graphene based copper oxide nanocomposites (CuOx/Graphene) for the catalytic applications (C-N cross coupling reaction). Briefly, Cu precursors were anchored on the graphite oxide(GO) sheets being exfoliated and oxidized from graphite powder. Two different crystalline structures of Cu2O and CuO on graphene and GO were prepared by annealing them in Ar and O2 environments, respectively. The morphological and electronic structures were systemically investigated using FT-IR, XRD, XPS, XAFS, and TEM. Here, we demonstrate that the catalytic performance was found to depend on oxidative states and morphological structures of CuOx graphene nanocomposites. The relationship between the structure of copper oxides and catalytic efficiency toward C-N cross coupling reaction will be discussed.

• Journal of the Korean Electrochemical Society
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• v.10 no.1
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• pp.1-6
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• 2007

Mercaptopropionic acid(mpa) has been used to make self-assembled monolayer(SAMs) on the surface of graphite electrode incorporating gold nano particles, which are subsequently modified with dopamine(dopa). Such modified electrodes haying types of Gr(Au)/mpa-dopa were employed in the electrocatalytic oxidation of NADH. The responses of such modified electrodes were studied in terms of electron transfer kinetics and reaction procedure in the reaction. The reaction of the surface immobilized dopa with NADH was studied using the rotating disk electrode technique and a value of $5.06{\times}10^5M^{-1}s^{-1}$ was obtained for the second-order rate constant in 0.1 M phosphate buffer(pH=7.0), which was a $EC_{cat}$ and kinetic controlled procedure. But, the modified electrodes were diffusion controlled reaction having $4.64{\times}10^{-4}cm^2s^{-1}$ of the coefficient within $10^{-3}s$ after starting the reaction.

• Journal of the Korean Ceramic Society
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• v.36 no.1
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• pp.21-29
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• 1999

The effects of density and pore size distribution of substrate in preparing SiC conversiton layer on graphite substrate were investigated. The chemical reaction for formation of SiC conversion layer was occurred at substrate surface or below surface through SiC gas infiltration. It was supposed that the pore size distribution required for the sufficient SiO gas infiltration and the continuous chemical reaction during conversion process was in the range of 1.0∼10.0$\mu\textrm{m}$. In the stress analysis of SiC layer with finite element method (FEM), the residual stress distribution due to thermal mismatch was shown. However, the compressive stress was measured in SiC layer by X-ray diffraction, it was presumed that the residual stress distribution of SiC layer was mainly influenced by the constraining effect of interlayer between SiC layer and graphite substrate, and the densification behaviro and the grain growth in SiC conversion layer.

• Journal of the Korean institute of surface engineering
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• v.54 no.4
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• pp.164-170
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• 2021

Vanadium redox flow batteries (VRFB) have emerged as large-scale energy storage systems (ESS) due to their advantages such as low cross-contamination, long life, and flexible design. However, Hydrogen evolution reaction (HER) in the negative half-cell causes a harmful influence on the performance of the VRFB by consuming current. Moreover, HER hinders V²⁺/V³⁺ redox reaction between electrode and electrolyte by forming a bubble. To address the HER problem, carbon nanotube/graphite felt electrode (CNT/GF) with oxygen functional groups was synthesized through the hydrothermal method in the H₂SO₄ + HNO₃ (3:1) mixed acid solution. These oxygen functional groups on the CNT/GF succeed in suppressing the HER and improving charge transfer for V²⁺/V³⁺ redox reaction. As a result, the oxygen functional group applied electrode exhibited a low overpotential of 0.395 V for V²⁺/V³⁺ redox reaction. Hence, this work could offer a new strategy to design and synthesize effective electrodes for HER suppression and improving the energy density of VRFB.