• Title/Summary/Keyword: Electrochemical Performance

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Research on the Gas Diffusion Electrode for the Brine Electrolysis (염수 전해용 가스확산 전극에 관한 연구)

  • Lee, D.H.;Lee, G.H.;Han, J.W.;Lim, J.T.;Lee, O.S.;Lee, J.D.
    • Journal of the Korean Electrochemical Society
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    • v.5 no.1
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    • pp.7-12
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    • 2002
  • The gas diffusion electrodes as oxygen cathodes f3r the brine electrolysis process were investigated. The gas diffusion electrode consists of a reaction layer, a gas diffusion layer, and a current distributor. The reaction layer was made from hydrophilic carbon black, hydrophobic carbon black, PTFE(polyterafluoroethylene), and Ag catalyst loaded by the silver mirror reaction or impregnation method. The gas diffusion layer was made from hydrophobic carbon black and PTFE, and Ni mesh was used as the current distributor in the reaction layer. The result that the gas diffusion electrode $(10wt\%\;Ag\;catalyst\;and\;20wt\%\;binder)$ manufactured by applying impregnation method to the carbon black f3r reaction layer showed the better performance was obtained from experiments. From the half-cell test, the measured overpotential of this oxygen cathode was about 700mV, And through the electrolysis experiment under the condition of $80^{\circ}C,\;32wt\%$ NaOH, and $300mA/cm^2$, the electrolysis voltage of this electrode was about 2.2 V, The gas diffusion electrodes manufactured in the present research were capable of continuous operations for three months.

Electrochemical Characteristics of Pt/PEM/Pt-Ru MEA for Water Electrolysis (수전해용 Pt/PEM/Pt-Ru MEA의 전기화학적 특성)

  • Kweon, Oh-Hwan;Kim, Kyung-Eon;Jang, In-Young;Hwang, Yong-Koo;Chung, Jang-Hoon;Moon, Sang-Bong;Kang, An-Soo
    • Transactions of the Korean hydrogen and new energy society
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    • v.19 no.1
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    • pp.18-25
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    • 2008
  • The membrane electrode assembly(MEA) was prepared by a nonequilibrium impregnation- reduction (I-R) method. Nafion 117 and covalently cross-linked sulfonated polyetherether with tungsto- phosphoric acid (CL-SPEEK/TPA30) prepared by our laboratory, were chosen as polymer electrolyte membrane(PEM). $Pt(NH_3)_4Cl_2$, $RuCl_3$ and reducing agent $(NaBH_4)$ were used as electrocatalytic materials. Electrochemical activity surface area(ESA) and specific surface area(SSA) of Pt cathodic electrode with Nafion 117 were $22.48m^2/g$ and $23.50m^2/g$ respectively under the condition of 0.8 M $NaBH_4$. But Pt electrode prepared by CL-SPEEK/TPA30 membrane exhibited higher ESA $23.46m^2/g$ than that of Nafion 117. In case of Pt-Ru anodic electrode, the higher concentration of Ru was, the lower potential of oxygen reduction and region of hydrogen desorption was, and Pt-Ru electrode using 10 mM $RuCl_3$ showed best properties of SSA $34.09m^2/g$ with Nafion 117. In water electrolysis performance, the cell voltage of Pt/PEM/Pt-Ru MEA with Nafion 117 showed cell property of 1.75 V at $1A/cm^2$ and $80{\circ}C$. On the same condition, the cell voltage with CL-SPEEK/TPA30 was the best of 1.73 V at $1A/cm^2$.

Corrosion Resistance of Blended Concrete and Its Application to Crack Healing (혼합 콘크리트의 부식 저항성과 균열 치유 적용)

  • Lee, Chang-Hong;Kim, Tae-Sang;Song, Ha-Won
    • Journal of the Korea Concrete Institute
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    • v.21 no.6
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    • pp.689-696
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    • 2009
  • In this study, electro-deposition method was applied to heal cracks in various blended concrete. The performance of the method was indirectly monitored by measuring impressed voltage, electrolyte, galvanic current monitoring, linear polarization resistance, and directly by image analysis of the cracks. The indirect and direct monitoring values are compared to develop guidelines for relating the indirect measures to actual crack healing. As a result, It was found that impressed voltage was convergence to 2.9V after 20000 minutes. From the galvanic current test results of artificial crack healing, the corrosion resistance showed that the order of 0.4 $>$ 0.6 $>$ 0.5 water to cement ratio. Furthermore, in view of binder, the corrosion resistance order was calculated OPC $>$ 60%GGBS $>$ 10%SF $>$ 30%PFA. Finally, It was found that 76.47% of healed crack surface calculated from the artificial crack healing technique using electrochemical deposition method.

Electrochemical Performance on the H3BO3 Treated Soft Carbon modified from PFO as Anode Material (음극소재로 PFO에서 개질된 붕산처리 소프트 카본의 전기화학적 성능)

  • Lee, Ho Yong;Lee, Jong Dae
    • Korean Chemical Engineering Research
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    • v.54 no.6
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    • pp.746-752
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    • 2016
  • In this study, soft carbon was prepared by carbonization of carbon precursor (pitch) obtained from PFO (pyrolysis fuel oil) heat treatment. Three carbon precursors prepared by the thermal reaction were 3903 (at $390^{\circ}C$ for 3 h), 4001 (at $400^{\circ}C$ for 1 h) and 4002 (at $400^{\circ}C$ for 2 h). After the prepared soft carbon was ground to a particle size of $25{\sim}35^{\circ}C$, the soft carbon was synthesised by the chemical treatment with boric acid ($H_3BO_3$). The prepared soft carbon were analysed by XRD, FE-SEM and XPS. Also, the electrochemical performances of soft carbon were investigated by constant current charge/discharge test, cyclic voltammetry and impedance tests in the electrolyte of $LiPF_6$ dissolved inorganic solvents (EC:DMC=1:1 vol%+VC 3 wt%). The coin cell using soft carbon of $25{\sim}35^{\circ}C$ with 3903 soft carbon ($H_3BO_3$/Pitch=3:100 in weight) has better initial capacity and efficiency (330 mAh/g, 82%) than those of other coin cells. Also, it was found that the retention rate capability of 2C/0.1C was 90% after 30 cycles.

Effect of Carbon Felt Oxidation Methods on the Electrode Performance of Vanadium Redox Flow Battery (탄소펠트의 산화처리 방법이 바나듐 레독스 흐름 전지의 전극 성능에 미치는 영향)

  • Ha, Dal-Yong;Kim, Sang-Kyung;Jung, Doo-Hwan;Lim, Seong-Yop;Peck, Dong-Hyun;Lee, Byung-Rok;Lee, Kwan-Young
    • Journal of the Korean Electrochemical Society
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    • v.12 no.3
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    • pp.263-270
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    • 2009
  • Carbon felt surface was modified by heat or acid treatment in order to use for the electrode of a redox-flow battery. Polymers on the surface of carbon felt was removed and oxygen-containing functional group was attached after the thermal treatment of carbon felt. Thermal treatment was better for the stability of the carbon structure than the acid treatment. Oxygen-containing functional group on the thermally treated carbon felt at 500$^{\circ}C$ was confirmed by XPS and elementary analysis. BET surface area was increased from nearly zero to 96 $m^2/g$. Thermally treated carbon felt at 500$^{\circ}C$ showed lower activation polarization than the thermally treated carbon felt at 400$^{\circ}C$ and the acid-treated carbon felt in the cyclicvoltammetry and polarization experiments. The thermally treated carbon felts at 400$^{\circ}C$ and 500$^{\circ}C$ and the acid-treated carbon felt was applied for the electrode to prepare vanadium redox flow battery. Voltage efficiencies of charge/discharge were 86.6%, 89.6%, and 96.9% for the thermally treated carbon felts at 400$^{\circ}C$ and 500$^{\circ}C$ and the acid-treated carbon felt, respectively.

Electrochemical Characterization of Hybrid Semiconductor-Based Dye-Sensitized Solar Cells (혼성반도체로 제조된 염료감응형 태양전지의 전기화학적 특성)

  • Lee, Sung-Kyu;Jeong, Eui-Gyung;Im, Ji-Sun;Lee, Young-Seak
    • Korean Chemical Engineering Research
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    • v.49 no.2
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    • pp.175-180
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    • 2011
  • In this study, the $TiO_{2}/V_{2}O_{5}$ hybrid semiconductors were prepared by mixing $TiO_{2}$ and $V_{2}O_{5}$, and a subsequent smash process to reduce the recombination of electron and improve the efficiency of solar cells. Dye-sensitized solar cells were constructed using the resultant hybrid semiconductor, and their electrochemical properties were also investigated. The photocurrent-voltage curve obtained with the cells indicated a significant increase in the efficiency from 2.9 to 5.7% by the factor of 2 compared to the result obtained only with $TiO_{2}$. It is believed that the introduction of $V_{2}O_{5}$ effectively transport electrons in the $TiO_{2}$ conduction band to FTO glass and suppress recombination with the dye and/or the electrolyte, thus yielding an efficient performance of the dye sensitized solar cell. The impedance values also indicated a decrease of resistance in the interface of $TiO_{2}$/dye/electrolyte supporting the constructive contributions of the smashed $TiO_{2}/V_{2}O_{5}$ hybrid semiconductors for the efficiency.

Prediction of Life Time of Ion-exchange Membranes in Vanadium Redox Flow Battery (바나듐 레독스 흐름전지용 이온교환막의 수명 예측)

  • Cho, Kook-Jin;Park, Jin-Soo
    • Journal of the Korean Electrochemical Society
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    • v.19 no.1
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    • pp.14-20
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    • 2016
  • Vanadium redox flow battery (VRFB) is an energy conversion device in which charging and discharging are alternatively carried out by oxidation and reduction reactions of vanadium ions with different oxidation states. VRFB consists of electrolyte, electrode, ion-exchange membrane, etc. The role of ion-exchange membranes in VRFB separates anolyte and catholyte and provides a high conductivity to hydrogen ions. Recently much attention has been devoted to develop ideal ion-exchange membranes for VRFB. A number of developed ion-exchange membranes should be evaluated to find out ideal ion-exchange membranes for VRFB. Long-term durability test is a crucial characterization of ion-exchange membranes for commercialization, but is very time-consuming. In this study, the life time prediction protocol of ion-exchange membranes in VRFB cell tests was developed through short-term single cell performance evaluation (real total operation time, 87.5 hrs) at three different current densities. We confirmed a decrease in test time up to 96.2% of real durability tests (expected total operation time, 2,296 hrs) and 5~6% of relative error discrepancy between the predicted and the real life time in a unit cell.

Perfluorinated Sulfonic Acid based Composite Membranes for Vanadium Redox Flow Battery (바나듐 레독스 흐름 전지를 위한 과불소화 술폰산 복합막)

  • Cho, Kook-Jin;Park, Jin-Soo
    • Journal of the Korean Electrochemical Society
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    • v.19 no.1
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    • pp.21-27
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    • 2016
  • Vanadium redox flow batteries (VRFBs) using the electrolytes containing various vanadium ions in sulfuric acid as supporting solution are one of the energy storage devices in alternatively charging and discharging operation modes. The positive electrolyte contains $V^{5+}/V^{4+}$ and the negative electrolyte $V^{2+}/V^{3+}$ depending on the operation mode. To prevent the mixing of two solutions, proton exchange membranes are mainly used in VRFBs. Nafion 117 could be the most promising candidate due to the strong oxidative property of $V^{5+}$ ion, but causes high crossover of electroactive species to result in a decrease in coulombic efficiency. In this study, the composite membranes using Nafion ionomer and porous polyethylene substrate were prepared to keep good chemical stability and to decrease the cost of membranes, and were compared to the properties and performance of the commercially available electrolyte membrane, Nafion 117. As a result, the water uptake and ionic conductivity of the composite membranes increased as the thickness of the composite membranes increased, but those of Nafion 117 slightly decreased. The permeability of vanadium ions for the composite membranes significantly decreased compared to that for Nafion 117. In a single cell test for the composite membranes, the voltage efficiency decreased and the coulombic efficiency increased, finally resulting in the similar energy efficiency. In conclusion, the less cost of the composite membranes by decreasing 6.4 wt.% of the amount of perfluorinated sulfonic acid polymer due to the introduction of porous substrate and lower vanadium ion permeability to decrease self-discharge were achieved than Nafion 117.

Fabrication and Evaluation of Si3N4-coated Organic/inorganic Hybrid Separators for Lithium-ion Batteries (Si3N4-코팅 유/무기 복합 분리막을 통한 리튬이온전지용 분리막의 제조 및 평가)

  • Yeo, Seung-Hun;Son, Hwa-Young;Seo, Myeong-Su;Roh, Tae-Wook;Kim, Gyu-Chul;Kim, Hyun-Il;Lee, Ho-Chun
    • Journal of the Korean Electrochemical Society
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    • v.15 no.1
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    • pp.48-53
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    • 2012
  • Polyethylene (PE) separator is the most popular separator for lithium-ion batteries. However, it suffers from thermal contraction and mechanical rupture. In order to improve the thermal/mechanical dimensional stabilities, this study investigated the effects of $Si_3N_4$ coating. SCS (Silicon-nitride Coated Separator) has been fabricated by applying 10 ${\mu}m$-thick $Si_3N_4$/PVdF coating on one side of PE separator. SCS exhibits enhanced thermal stability over $100{\sim}150^{\circ}C$: its thermal shrinkage is reduced by 10~20% compared with pristine PE separator. In addition, SCS shows higher tensile strength than PE separator. Employing SCS hardly affects the C-rate performance of $LiCoO_2$/Li coin-cell, even though its ionic conductivity is somewhat lower than that of PE separator.

Surface Modification of Nafion by Layer-by-Layer Self-Assembled Films of Polyaniline and Sulfonated Poly(ether sulfone) for Direct Methanol Fuel Cell (직접 메탄올 연료전지용 나피온 막의 폴리아닐린/Sulfonated Poly(ether sulfone) 다층 자기조립 박막에 의한 표면 개질)

  • Ok, Jeong-Rim;Kim, Dong-Wook;Lee, Chang-Jin;Kang, Yong-Ku
    • Journal of the Korean Electrochemical Society
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    • v.11 no.4
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    • pp.256-261
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    • 2008
  • In this study, Nafion membrane was modified to prevent methanol crossover by layer-by-layer self assembly using polyaniline (PANi) as a polycation and sulfonated poly(ether sulfone) (SPES) as a polyanion onto the Nafion surface. Since PANi and SPES possess thermal and chemical stability and rigid backbone, their layer-by-layer self-assembled films on the Nafion are expected to reduce methanol permeability and to increase mechanical stability. UV-Vis absorption spectroscopy verified a linear build-up of the multilayers of PANi and SPES. We found that the thickness per bilayer was about 10 nm by TEM measurement. Although modified Nafion membrane exhibited 15% decrease of proton conductivity, it reduceded 67% of methanol permeability compared to that of the pristine Nafion membrane, resulting in 2.5 times larger selectivity. At the performance test of the fuel cell using 5M methanol as a fuel, the modified Nafion membrane showed 2.4 times higher maximum power density at $30^{\circ}C$ and 1.4 times larger at $60^{\circ}C$ than the pristine Nafion.