• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.64-72
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• 2017

A series of Pt-based ${\gamma}-Al_2O_3$ catalysts promoted with several alkali and alkaline earth metals were prepared by a wet impregnation method. We confirmed that the addition of Na to $Pt/{\gamma}-Al_2O_3$ could cause a change in the oxidation state of Pt through an electronegative gap between Pt and Na atom, and increase the ratio of the metallic Pt. The metallic Pt species made by adding an optimum Na content improved the adsorption of NO species on the catalyst surface and restrained the oxidation of $CH_4$ to $CO_2$. When molar ratio of Na/Pt was 4.0, the highest catalytic activity could be obtained.

• Journal of Hydrogen and New Energy
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• v.19 no.4
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• pp.305-312
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• 2008

ZnO/Zn redox cycle is the one of the promising thermochemical cycles for hydrogen production via water splitting with high temperature heat source like a concentrated solar energy. This paper reports the particle size effect of Zinc on water splitting behavior. Water splitting reaction experiments were carried out at isothermal conditions of 350 and 400$^{\circ}C$ in TGA (Thermo Gravimetric Analyzer) using four commercial Zinc powders (nano, <10 ${\mu}m$, <150 ${\mu}m$ and $150{\sim}600\;{\mu}m$ particle sizes). Before the experiments, average particle size of Zinc powders was analyzed by PSA (Particle Size Analysis). After the experiments, XRD (X-Ray Diffraction) and SEM (Scanning Electron Microscope) analyses were conducted on the samples. The experimental results showed that particle size had a effect on the conversion of Zinc to ZnO. Zinc conversion was increased, as the particle size decreased. Especially, the nano size particles were aggregated and the particle's morphology changed on the surface during hydrolysis reaction.

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.901-907
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• 2001

Magnetite was synthesized using $0.2M-FeSO_4{\cdot}7H_{2}O$ and 0.5 M-NaOH by air oxidation method for carbon dioxide decomposition to carbon. The carbon dioxide decomposition was successfully carried out after reduction of ${Fe_3}{O_4}$ for 2 hrs using hydrogen gas. The carbon dioxide decomposition at 325, 350, 375, 400, $425^{\circ}C$, 88% was the highest at $350^{\circ}C$ and the activation energy of ${Fe_3}{O_4}$ in carbon dioxide decomposition was 30.96 kJ/mol. After $CO_2$ decomposition, the carbon of surface of catalyst reacted with hydrogen produced methane.

• Journal of the Korean Electrochemical Society
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• v.17 no.3
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• pp.156-163
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• 2014

In this study, we tried to improve the cycling performance of lithium-ion batteries by suppressing decomposition of the electrolyte solution containing fluorsilane-based additive. Trifluoropropyltrimethoxysilane was electrochemically oxidized and reduced prior to the decomposition of the liquid electrolyte composed of lithium salt and carbonate-based organic solvent. Thus, the stable solid electrolyte interphase (SEI) layer on both negative electrode and positive electrode was formed, and it was confirmed that the cycling performance of lithium-ion batteries assembled with electrolyte solution containing 5 wt.% trifluoropropyltrimethoxysilane was the mostly enhanced. The products formed on electrodes were analyzed by the SEM and XPS analysis, and it was demonstrated that trifluoropropyltrimethoxysilane can be one of the promising SEI-forming additives.

• Polymer(Korea)
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• v.37 no.2
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• pp.218-224
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• 2013

Graphene oxide (GO) was prepared by the Hummers and Offeman method from graphite. Two different types of functionalized graphene sheets (FGSs) were synthesized by using GO. Hexamethylamine (HDA) substituted vertically to the graphene sheet (Ver-HDA-GS) was synthesized from HDA and epoxy group in GSs. Whereas, horizontally substituted hexadecanol (HDO) to the GS(Hor-HDO-GS) was synthesized from HDO and alcohol groups via reduced GO (RGO), respectively. The structures of the GO, RGO, Ver-HDA-GS, and Hor-HDO-GS were identified by Fourier transform infrared (FTIR). In addition, we examined the thermal stability and morphology. Atomic force microscope (AFM) disclosed that Ver-HDA-GS consisted of one- or two-layer graphene regions. However, the Ver-HDA-GS layers showed average thickness of 1.76 nm. The thermal stabilities of the FGSs were better than those of the GO and RGO. The Ver- HDA-GS was well dispersed in common solvents such as dimethyl sulfoxide (DMSO), toluene, chloroform, and decalin.

• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1082-1089
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• 1998

To obtain fine dispersion of Ag particles in $YBa_2$$Cu_3$$O_{7-y}$ (123) superconductors, 123 samples were made by pyrophoric synthetic method using malic acid and the subsequent solid- state reaction. As the pyrophoric synthetic powder was used as a precursor material, fine 123 powder of submicron size was produced in a short reaction time. The added $Ag_2$O was converted to metallic Ag during Pyrophoric reaction and it accelerated both the formation of 123 phase and the grain growth via the enhanced mass transfer. The Ag particles of the sample sintered using the pyrephoric synthetic powder were more finely dispersed in the 123 matrix, compared to those of the sample sintered using the mechanically mixed powder, attributing to the improvement of the superconducting properties.

• Journal of the Korean Electrochemical Society
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• v.17 no.4
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• pp.209-215
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• 2014

We report on the electrocatalytic activities at Pt nanostructure surfaces electrodeposited with different deposition charges on indium tin oxide electrodes for oxygen reduction and methanol oxidation reactions. The surface properties of Pt nanostructures depending on deposition charges were characterized by scanning electron microscopy, electrochemical surface area measurement, X-ray diffraction, and CO stripping analysis, which were correlated to the electrocatalytic activities. Pt nanostructures with deposition charge of 0.03 C exhibited the highest electrocatalytic activity for oxygen reduction and methanol oxidation. The sharp sites of Pt nanostructure and the presence of highly active facet play a key role, whereas the electrochemical surface area does not significantly affect the electrocatalytic activity. The results obtained in this work with regard to the dependence of electrocatalytic activity on the variation of the Pt nanostructures will give insights into the development of advanced electrocatalytic systems.

• Journal of the Korean Chemical Society
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• v.63 no.5
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• pp.327-334
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• 2019

Inhibition effects of cysteine(Cys), methionine(Met), and histidine(His) on the corrosion of cobalt were investigated in deaerated 0.5 M HCl and 0.5 M $H_2SO_4$ solution. All the inhibition efficiency (IE) in the amino acids for the cobalt corrosion depended on the mixed inhibition. However, IE in the solution of $H_2SO_4$ depended more on the anodic and in the solution of HCl on the cathodic inhibition. Amino acid adsorption process on cobalt surface in the solution can be explained by modified Langmuir isotherm. The molecules of histidine dissolved in both of the solution were physically adsorbed due to the electrostatic interaction between the surface of {$Co-Cl^{-{\delta}}$} and the {$-NH_3{^+}$} or {$-NH^+=$} of His. However the other cases of adsorption in this investigation can be explained by chemical adsorption between the empty d-orbital of Co and the lone pair of electron in S-atom in Cys and Met.

• Economic and Environmental Geology
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• v.50 no.3
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• pp.215-224
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• 2017

Arsenic (As) is known to be the most toxic element and frequently detected in groundwater environment. Inorganic As exists as arsenite [As(III)] and arsenate [As(V)] in reduced and oxidized environments, respectively. It has been reported that the toxicity of arsenite is much higher than that of arsenate and furthermore arsenite shows relatively higher mobility in aqueous environments. For this reason, there have been numerous researches on the process for oxidation of arsenite to arsenate to reduce the toxicity of arsenic. In particular, photooxidation has been considered to be simple, economical, and efficient to attain such goal. This study was conducted to evaluate the applicability of naturally-occurring goethite as a photocatalyst to substitute for $TiO_2$ which has been mostly used in the photooxidation processes so far. In addition, the effects of several factors on the overall performance of arsenite photocatalytic oxidation process were evaluated. The results show that the efficiency of the process was affected by total concentration of dissolved cations rather than by the kind of those cations and also the relatively higher pH conditions seemed to be more favorable to the process. In the case of coexistence of arsenite and arsenate, the removal tendency by adsorption onto goethite appeared to be different between arsenite and arsenate due to their different affinities with goethite, but any effect on the photocatalytic oxidation of arsenite was not observed. In terms of effect of humic acid on the process, it is likely that the higher concentration of humic acid reduced the overall performance of the arsenite photocatalytic oxidation as a result of competing interaction of activated oxygen species, such as hydroxyl and superoxide radicals, with arsenite and humic acid. In addition, it is revealed that the injection of oxygen gas improved the process because oxygen contributes to arsenite oxidation as an electron acceptor. Based on the results of the study, consequently, the photocatalytic oxidation of aqueous arsenite using goethite seems to be greatly feasible with the optimization of process.

• Korean Chemical Engineering Research
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• v.44 no.4
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• pp.404-409
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• 2006

The catalytic combustion of toluene over Pd-Cu/USY zeolite has been examined by using FT-IR spectroscopy in a closed system under dry and humid conditions. The catalytic combustion of toluene (700 ppmv) in the temperature range of $80-220^{\circ}C$ has been investigated by using a fixed bed reactor. The Pd-Cu/USY catalyst showed the highest catalytic performance with respects to the PdO-CuO/USY and Pd/USY. Comparing to $PdO/Al_2O_3$ catalysts, the slight improvement in conversion was observed over PdO/USY catalysts under humid condition since USY zeolite is hydrophobic substrate and water give an additional oxygen source to zeolite surface like oxygen. The reduced catalysts showed more enhanced catalytic activity due to the reduced activation energy of combustion of toluene than oxidized catalysts such as PdO/USY and PdO-CuO/USY.