• Title/Summary/Keyword: Activated carbon electrode

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Synthesis and Electrochemical Characteristics of Spherical Li4Ti5O12/CNT Composite Materials for Hybrid Capacitors

  • Yang, Joeng-Jin;Kim, Yu-Ri;Jeong, Moon-Gook;Yuk, Yong-Jae;Kim, Han-Joo;Park, Soo-Gil
    • Journal of Electrochemical Science and Technology
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    • v.6 no.2
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    • pp.59-64
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    • 2015
  • Spherical Li4Ti5O12 and Li4Ti5O12 carbon nanotube (CNT) composites were synthesized using a colloid system. The electrochemical properties of the composites were thoroughly examined to determine their applicability as hybrid capacitor anodes. The electrical conductivity of the spherical Li4Ti5O12-CNT composite was improved over that of the spherical Li4Ti5O12 composite. The synthesized composites were utilized as the anode of a hybrid capacitor, which was assembled with an activated carbon (AC) positive electrode. The CNTs attached on the spherical Li4Ti5O12 particles contributed to a 51% reduction of the equivalent series of resistance of the Li4Ti5O12-CNTs/AC hybrid capacitor compared to the Li4Ti5O12/AC hybrid capacitor. Moreover, the Li4Ti5O12-CNTs/AC hybrid capacitor showed a larger capacitance than the Li4Ti5O12/AC hybrid capacitor; specifically, the Li4Ti5O12-CNT/AC hybrid capacitor showed 1.6 times greater capacitance at 40 cycles with a 10 mA cm−2 loading current density.

Electrochemical Performance of Composite Active Materials (Activated Carbon + $LiCoO_2$) Electrode (혼합 활물질 (활성탄소 + $LiCoO_2$) 전극의 전기화학적 특성)

  • Kim, Ick-Jun;Jeon, Min-Jae;Yang, Sun-He;Moon, Seoung-In;Kim, Hyun-Soo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.06a
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    • pp.497-497
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    • 2007
  • 활성탄소를 양쪽 전극에 사용하는 전기이중층 커패시터는 고출력 특성과 반영구적인 cycle 수명인 장점을 가지고 있는 반면, 단위 중랑 또는 부피 당 용량이 작아 메모리 백업용 보조전원으로서의 활용에 그치고 있다. 이를 보완하기 위하여 최근에는 앙쪽의 전극에 충방전 메카니즘을 달리하는 비대칭 전극 설계기술을 기반으로 하는 하이브리드 커패시터가 개발되었고, 에너지밀도로서는 유기계 전해액에서 약 15-20 Wh/kg를 가지는 것으로 보고되고 있다. 본 연구메서는 양극의 활성탄소에 비용량이 상대적으로 큰 LiCo02 분말을 혼합한 하이브리드 전극의 제조 및 전기화학적 특성을 조사하였다. 이때 $LiCoO_2$ 분말의 혼합 종량비의 영향에 의한 전극 부피 당 용량(mAh/cc)의 변화와 $LiCoO_2$ 분말의 입자 크기에 의한 하이브리드 전극의 출력 특성을 조사하였다. $LiCoO_2$ 분말은 불밀을 이용하여 입자크기를 조절하였고, 각각의 입자크기를 가지는 LiCoO2 분말을 활성탄소와 함께 혼합하여 혼합 활물질 : Carbon black : PTFE의 중량비가 90 : 5 : 5가 되도록 sheet 전극을 제조하였다. 제조한 전극을 양극에, Li foil을 음극에, 전해액을 LiPF6 in EC DMC를 사용하여 코인셀을 제조하고 전기화학적 특성은 MACCOR 충방전기를, AC 저항은 AC impedance를 각각 사용하여 평가하였다. 활성탄소에 $LiCoO_2$ 분말의 첨가 중량비가 증가할수록 전극 부피 당 용량은 증가하였으나, 원료 상태의 $LiCoO_2$ 분말의 첨가에서는 코인셀의 전극 저항은 첨가 중량에 따라 단순 증가하였다. 그러나 미세 $LiCoO_2$ 분말을 첨가할 경우, 20%의 첨가에서 전극 저항은 활성탄소 만을 사용한 전극과 동등한 전극저항을 나타내고 충방전 cycle 특성도 개선되는 것을 확인하였다.

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Selective Oxidation of 2,6-di-tert-butylphenol and Electrochemical Properties by Oxygen Adducted Tetradentate Schiff Base Cobalt (Ⅲ) Activated Catalysts in Aprotic Solvents (비수용매에서 산소 첨가된 네자리 Schiff Base Cobalt(Ⅲ) 활성 촉매들에 의한 2,6-di-tert-butylphenol의 선택 산화와 전기화학적 성질)

  • Jo, Gi Hyeong;Choe, Yong Guk;Ham, Hui Seok;Kim, Sang Bok;Seo, Seong Seop
    • Journal of the Korean Chemical Society
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    • v.34 no.6
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    • pp.569-581
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    • 1990
  • It is generated in DMF by activated catalysts of superoxo cobalt(III) complex, such as [Co(III)(Schiff base)(L)]O$_2$ (Schiff base; SED, SOPD and o-BSDT, L; DMF and Py) which mole ratio of oxygen to metal is 1:1 that oxidation major product of 2,6-di-tert-butylphenol by homogeneous oxidatve catalysts of oxygen adducted tetradentate Schiff base cobalt(III) is 2,6-ditert-butylbenzoquinone (BQ). And oxidation product of 3,3',5,5'-tetra-tert-butyldiphenoquinone (DPQ) is generated by activated catalysts such as $\mu$-peroxo cobalt(III) complex; $[Co(III)(SND)(L)]_2$$O_2$ (L; DMF and Py) which mole ratio of oxygen to metal is 1:2. It is difficult to identify these homogeneous activated catalysts such as superoxo and $\mu$-peroxo cobalt(III) complexes in DMF and DMSO solvents. But we can identify by P.V.T method of the oxygen absorption in pyridine solvent and by the reduction process occurred to four steps including prewave of O$_2$- in 1:1 oxygen adducted superoxo cobalt(III) complexes and three steps not including prewave of O$_2$- in 1:2 oxygen adducted $\mu$-peroxo cobalt(III) complexes by the cyclic voltammetry with glassy carbon electrode in 0.1 M TEAP as supporting electrolyte solutidn.

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$CO_2$ Sensing Characteristics of Carbon-nanofibers Based on Effects of Porosity and Amine Functional Group (다공성 및 아민 작용기에 따른 탄소나노섬유의 $CO_2$ 감응특성)

  • Kim, Jong Gu;Kang, Seok Chang;Shin, Eunjeong;Kim, Da Young;Lee, Jin Hee;Lee, Young-Seak
    • Applied Chemistry for Engineering
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    • v.23 no.1
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    • pp.47-52
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    • 2012
  • Porous carbon nanofibers were prepared as a gas sensor electrode to study the $CO_2$ sensing property based on effects of porosity and introduced amine functional groups. Electrospun fibers were obtained by using electrospinning method with polyacrylonitrile precursor and they were treated by the thermal treatment and chemical activation. Amine functional groups were introduced by the liquid state treatment using diethylenetriamine. The specific surface area increased up to $2000m^2/g$ by the chemical activation. The Introduced amine functional group was identified using FT-IR spectroscopy. $CO_2$ gas sensing property was improved as four folds via introduced amine functional groups on the activated carbon nanofiber. In conclusion, the gas sensing property was improved based on the developed porosity by the chemical activation and the chemical attraction of $CO_2$ gas by introduced functional groups.

Application of Capacitive Deionization for Desalination of Mining Water (광산수의 탈염을 위한 축전식 탈염기술의 적용)

  • Lee, Dong-Ju;Kang, Moon-Sung;Lee, Sang-Ho;Park, Jin-Soo
    • Journal of the Korean Electrochemical Society
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    • v.17 no.1
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    • pp.37-43
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    • 2014
  • In this study, capacitive deionization (CDI) was introduced for desalination of mining water. Ion-exchange polymer coated carbon electrodes (IEE) were used in CDI to desalt mining water. The CDI performance using the IEE for desalination of mining water was carried out and then was compared with that using general carbon electrodes without ion-exchange polymer coating (GE). Moreover, to investigate the effect of the concentration of influent solutions on CDI performance, the CDI performance using the IEE for desalination of brackish water (NaCl 200 ppm) was also performed and analyzed. As a result, the higher salt removal efficiency, rate and the lower energy consumption in the CDI process using the IEE and mining water were obtained compared with those using the GE and mining water. It is mainly due to higher non-Faradaic current, low ohmic resistance of the influent, overlapping effect of electric double layers in micropore of the electrode. In addition, the CDI process using the IEE and brackish water shows much higher salt removal efficiency and lower salt removal rate than that using the IEE and mining water. This results from the lower concentration (i.e., higher ohmic resistance) and salt amount of the influent.

HI concentration by EED for the HI decomposition in IS process (IS 프로세스의 HI 분해반응공정을 위한 전해 - 전기투석(EED) HI 농축)

  • Hong, Seong-Dae;Kim, Jeong-Geun;Lee, Sang-Ho;Choi, Sang-Il;Bae, Ki-Kwang;Hwang, Gab-Jin
    • Transactions of the Korean hydrogen and new energy society
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    • v.17 no.2
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    • pp.212-217
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    • 2006
  • An experimental study on Electro-electrodialysis (EED) for IS (Iodine-Sulfur) process which is well known as hydrogen production system was carried out for the HI concentration from HIx (HI: $H_2O$ : $I_2$ = 1 : 5 : 1) solution. The polymer electrolyte membrane and the activated carbon cloth were adopted as a cation exchange membrane and electrode, respectively. In order to evaluate the temperature effect about HI concentration in fixed molar ratio, three case of temperature were selected to $60^{\circ}C$, $90^{\circ}C$ and $120^{\circ}C$. The electro-osmosis coefficient and transport number of proton have been changed from 1.95 to 1.21 (mol/Faraday) and 0.91 to 0.76, respectively as temperature increase from $60^{\circ}C$ to $120^{\circ}C$. It can be realized that the HI mole fraction in final stage of EED experiments already over the quasi-azeotrope composition.

Preparation of Polymer Gel Electrolyte for EDLCs using P(VdF-co-HFP)/PVP (P(VdF-co-HFP)/PVP를 이용한 EDLC용 고분자 겔 전해질의 제조)

  • Jung, Hyun-Chul;Jang, In-Young;Kang, An-Soo
    • Applied Chemistry for Engineering
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    • v.17 no.3
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    • pp.243-249
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    • 2006
  • Porous polymer gel electrolytes (PGEs) based on poly(vinylidenefluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) as a polymer matrix and polyvinylpyrolidone (PVP) as a pore-forming agent were prepared and electrochemical properties were investigated for an electric double layer capacitor (EDLC) in order to increase a permeability of an electrolyte into the PGE. Propylene carbonate (PC) and ethylene carbonate (EC) as plasticizers, and tetraethylammonium tetrafluoroborate ($TEABF_4$) as a supporting salt for the PGE were used. EDLC unit cells were assembled with the PGE and electrode comprising BP-20 and MSP-20 as activated carbon powders, Super P as a conducting agent, and P(VdF-co-HFP)/PVP as a mixed binder. Ion conductivity of PGEs increased with an increased PVP content and was the best at 7 wt% PVP, whereas electrochemical characteristics such as AC-ESR of unit cell were better in 3 wt%. And electrochemical characteristics of the unit cell with PGE were the best at a 33 : 33 weight ratio of PC to EC. Specific capacitance of a mixed plasticizer system of PE and EC was higher than that of pure PC. Ion conductivity of PGEs with a film thickness of $20{\mu}m$ was higher, but electrochemical characteristics of unit cells were higher for a $50{\mu}m$ membrane thickness. Also, the unit cell has shown the highest capacitance of 31.41 F/g and more stable electrochemical performance when PGE and electrode were hot pressed. Consequently, the optimum composition ratio of PGE for EDLCs was 23 : 66 : 11 wt% such as P(VdF-co-HFP) : PVP = 20 : 3 wt% and PC : EC = 44 : 22 wt%. In this case, $3.17{\times}10^{-3}S/cm$ of ion conductivity was achieved at the $50{\mu}m$ thickness of PGE for EDLCs. And the electrochemical characteristics of unit cells were $2.69{\Omega}$ of DC-ESR, 28 F/g of specific capacitance, and 100% of coulombic efficiency.

Selective Oxidation of 2,6-di-tert-butylphenol by Oxygen Adducted Pentadentate Schiff Base Cobalt (Ⅱ) Activated Catalysts and Electrochemical Properties of Cobalt (Ⅱ) Catalysts in Aprotic Solvents (비수용매에서 산소첨가된 다섯자리 Schiff Base Cobalt (Ⅱ) 활성촉매들에 의한 2,6-di-tert-butylphenol의 선택산화와 전기화학적 성질)

  • Chjo, Ki-Hyung;Choi, Yong-Kook;Kim, Sang-Bock;Lee, Song-Ju;Kim, Jong-Soon
    • Journal of the Korean Chemical Society
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    • v.35 no.6
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    • pp.689-698
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    • 1991
  • Activated oxidation catalysts are generated by the treatment of pentadentate Schiff base cobalt(Ⅱ) complexes with the oxygen saturated DMF solution. Oxidation of 2,6-di-tert-butylphenol by homogeneous oxidation catalysts of superoxo type pentadentate schiff base cobalt(Ⅲ) complexes yields 2,6-di-tert-butylbenzoquinone(BQ) as a major product. And $O_2$/Co mole ratio of homogeneous oxidative catalysts such as [Co(Ⅲ)(sal-DET)]$O_2$ and [Co(Ⅲ)(sal-DPT)]$O_2$by PVT method of the oxygen absorption in DMSO and pyridine solution was 1:1, 1:1.52 in DMF solution and ${\mu}$-peroxo type cobalt(Ⅲ) complexes formed at solid state. The redox reaction processes of superoxo type cobalt(Ⅲ) complexes as homogeneous oxidation catalysts were investigated by cyclic voltammetry and DPP method at a glassy carbon electrode. As a result of electrochemical measurements the reduction processes of oxygen adducted superoxo type cobalt(Ⅲ) complexes occurred to four steps including prewave of $O_2$-in 0.1M TEAP-DMSO and 0.1 M TEAP-Pyridine as supporting electrolyte solution.

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Evaluation of the Stability of Oxidation-Reduced Potential (ORP) Using the Filter of the Alkaline Water (알칼리 환원수 필터의 산화환원전위 안정화 평가)

  • Nam, Sangyep;Kwon, Yunjung
    • Journal of the Institute of Electronics and Information Engineers
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    • v.53 no.8
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    • pp.129-135
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    • 2016
  • This study is about ionic water generator filter Recently, a lot of people feel deep interest in health and drinking water. Evaluation of the stability of oxidation-reduced potential (ORP) using the filter of the alkaline water. This study utilizes the three filter of activated carbon, UF, carbon block in alkaline reduced water equipment. Passing the water to the filter is evaluated that the OPR values are stability in accordance with the change of the volume in the bucket. Alkaline reduced water equipment is a system that has the function of making the water reduction. This system is the values of the human body beneficial minerals and ORP are made in the functional water has a very low value than general water. Which has passed through the filter the water in the water negative ions and positive ions through the electrolytic. After electrolysis, the cathode side by water, including $Ca^+$, $K^+$, $Mg^+$, $Na^+$ water gets Alkaline Reduced Water containing the minerals beneficial to the human body. A positive electrode side is made of the organic materials that have an anion such as chlorine (Cl), phosphorus (P), sulfur(S). This experiment uses the Alkaline Reduced Water to adjust the magnitude of the voltage of the electrolysis in the Alkaline Reduced Water. That is 1st step(pH8) 2nd step (pH8.5) 3th step (pH9), 4th step (pH9.5) in the Alkaline Reduced Water and -1st step (pH6.0), -2nd step (pH5.0) used as the acidic oxidation water. When the water passes through the three filter in this system was evaluated whether the ORP values are changed and stabilized. When about 100 liters of water passing through the filter was confirmed that the ORP values are stability and evaluation.

Structures and Double Layer Performances of Carbons Pyrolized from Carbon Oxides (산화탄소로부터 열분해한 탄소의 구조 및 전기이중층 거동)

  • Kim, Ick-Jun;Yang, Sunhye;Jeon, Min-Je;Moon, Seong-In;Kim, Hyun-Soo;An, Kye-Hyeok
    • Applied Chemistry for Engineering
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    • v.18 no.5
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    • pp.522-526
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    • 2007
  • Structural features and electrochemical performances of cokes pyrolized from oxidized cokes were examined, and compared with KOH-activated coke. Needle cokes ($d_{002}=3.5{\AA} $), having a graphene layer structure, were changed to a single phase of graphite oxide after oxidation treatment with an acidic solution having an $NaCLO_3$/needle coke composition ratio of above 7.5, and the inter-layer distance of the oxidized coke was expanded to $6.9{\AA} $ with increasing oxygen content. After heating at $200^{\circ}C$, the oxidized coke was pyrolized to the graphene layer structure with inter-layer distance of $3.6{\AA} $. However, the change of the inter-layer distance of the needle coke was not observed in the KOH activation process. On the other hand, an intercalation of electrolyte ions into the pyrolized coke, observed at first charge, occurred at 1.0 V, in which the value was lower than that of KOH-activation coke. The cell capacitor using pyrolized coke exhibited a lower internal resistance of $0.57{\Omega}$ in 1 kHz, and a larger capacitance per weight and volume of 30.3 F/g and 26.9 F/ml at the two-electrode system in the potential range 0~2.5 V than those of the cell capacitor using KOH-activation of coke. This better electrochemical performance may be associated with structure defects in the graphene layer derived from the process of the inter-layer expansion and shrinkage.