• Title, Summary, Keyword: Carbon felt

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Surface Treatment with Alkali Solution of Carbon Felt for Vanadium Redox Flow Battery (바나듐레독스흐름전지용 카본펠트전극의 알칼리용액을 이용한 표면개질)

  • KIM, SUNHOE;LEE, KEON JOO
    • Transactions of the Korean hydrogen and new energy society
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    • v.27 no.4
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    • pp.372-377
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    • 2016
  • The carbon felt used as the electrode of vanadium redox flow battery (VRFB) requires imprived electrochemical activity for better battery performance and efficiencies. Many efforts have been tried to improve electrochemical activity of the carbon felt as electrodes. In this study the alkali solution, KOH, is applied on surface treatment of the carbon felt electrode. The carbon felts were treated with KOH under room temperature and $80^{\circ}C$. The isopropyl alcohol was applied to improve wettability of the carbon felt during KOH treatment. The KOH treated carbon felt was analyzed by using the X-ray photoelectron spectroscopy (XPS). The XPS analysis of carbon felt electrode revealed on increase in the overall surface oxygen content of the carbon felts after KOH treatment. Also, cyclic voltametry tests showed electrochemical characteristics enhancement of the carbon felt.

Electrochemical Enhancement of Carbon Felt Electrode for Vanadium Redox Flow Battery with Grephene Oxide (산화그레핀을 이용한 바나듐레독스흐름전지용 카본펠트전극의 표면개질을 통한 전기화학적 활성개선)

  • LEE, KEON JOO;KIM, SUNHOE
    • Transactions of the Korean hydrogen and new energy society
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    • v.28 no.2
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    • pp.206-211
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    • 2017
  • Carbon felt electrode for the vanadium redox-flow battery (VRFB) has been studied to see the effect of grephene oxide (GO) treatment on the surface of the carbon felt electrode. In this paper, surface of carbon felt electrodes were treated with various concentrations of grephene oxide. Electrochemical analysis, cyclic voltammetry (CV), was performed to investigate redox characteristics as electrode for VRFB. Also the effect of GO on the introduction of functional group on the surface of carbon felt electrodes were investigated using X-ray photoelectron spectroscopy (XPS), which discovered increase in the overall functional group content on the surface of carbon felts.

Electrochemical Oxidation of Carbon Felt for Redox Flow Battery (Redox flow battery용 carbon felt 전극의 전기화학적 산화)

  • Jung, Young-Guan;Hwang, Gab-Jin;Kim, Jae-Chul;Ryu, Cheol-Hwi
    • Transactions of the Korean hydrogen and new energy society
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    • v.22 no.5
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    • pp.721-727
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    • 2011
  • All vanadium redox-flow battery (VRFB) has been studied actively as one of the most promising electrochemical energy storage systems for a wide rage of applications such as electric vehicles, photovoltaic arrays, and excess power generated by electric power plants at night time. In this study, carbon felt electrodes were treated by electrochemical oxidation with KOH, and the cyclic voltammetry were studied in order to investigate redox reactivity of vanadium ion species with carbon felt electrodes. Besides the effect of electrochemical oxidation on the surface chemistry of carbon felt electrodes were investigated using the X-ray photoelectron spectroscopy (XPS). After electrochemical oxidation, XPS analysis of PAN based GF20-3 carbon felt electrode revealed on increase in the overall surface oxygen content of the carbon felts after electrochemical oxidation. Redox reaction characteristics using cyclic voltammetry (CV) were ascertained that the electrochemical treated electrode were more reversible than the untreated electrode.

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.

Porous Electrodes with Lower Impedance for Vanadium Redox Flow Batteries

  • Park, Su Mi;Kim, Haekyoung
    • Korean Chemical Engineering Research
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    • v.53 no.5
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    • pp.638-645
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    • 2015
  • Vanadium redox flow batteries (VRFBs) have been investigated for their potential utility as large energy storage systems due to their advantageous performances in terms of long cycle life, high energy efficiency, low cost, and flexible design. Carbon materials are typically used as electrodes in redox reactions and as a liquid electrolyte support. The activities, surface areas, and surface morphologies of porous carbon materials must be optimized to increase the redox flow battery performance. Here, to reduce the resistance in VRFBs, surface-modified carbon felt electrodes were fabricated, and their structural, morphological, and chemical properties were characterized. The surface-modified carbon felt electrode improved the cycling energy efficiencies in the VRFBs, from 65% to 73%, due to the improved wettability with electrolyte. From the results of impedances analysis with proposed fitting model, the electrolyte-coupled polarization in VRFB dramatically decreased upon modification of carbon felt electrode surface. It is also demonstrated that the compressibility of carbon felt electrodes was important to the VRFB polarization, which are concerned with mass transfer polarization. The impedance analysis will be helpful for obtaining better and longer-lived VRFB performances.

Electrochemical Studies of Carbon Felt Electrode Modified Under Airless Conditions for Redox Flow Batteries

  • Noh, Tae Hyoung;Kim, Min Young;Kim, Da Hye;Yang, Seung Hoon;Lee, Jong Ho;Park, Hong Sik;Noh, Hee Sook;Lee, Moo Sung;Kim, Ho Sung
    • Journal of Electrochemical Science and Technology
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    • v.8 no.2
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    • pp.155-161
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    • 2017
  • Carbon felts were prepared under various thermal conditions to improve the electrochemical properties of vanadium redox flow batteries. The number of C-O and/or C-OH functional groups on the surface of the electrodes treated under airless conditions was much larger than that of the untreated and partially oxygen-treated electrodes. The carbon felt treated under airless conditions had the lowest surface area. The overall kinetic properties of the redox reaction were greatly improved for the carbon felt treated under airless conditions; i.e., the reversibility of the anodic and cathodic reactions associated with the $VO_2{^+}/VO^{2+}$ couple became more reversible. Single-cell tests indicated that the carbon felt exhibited an excellent discharge capacity of $3.1Ah{\cdot}g^{-1}$ at $40mA{\cdot}cm^{-2}$, and the corresponding Coulombic, voltage, and energy efficiencies were 89.5%, 91.8%, and 82.2%, respectively.

Elimination Effect of Formaldehyde, Acetaldehyde and Total Volatile Organic Compounds from Car Felts using Nano-carbon Materials

  • Cho, Wan-Goo;Park, Seung-Gyu;Kim, Hyung-Man
    • Journal of the Korean Applied Science and Technology
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    • v.26 no.1
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    • pp.38-44
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    • 2009
  • We proposed the new nano-carbon ball (NCB) materials for eliminating the total volatile organic compounds(TVOCs) from the felt which is built in the car. The concentrations of acetaldehyde and formaldehyde of the original felts were varied upon the different production lots. Acetaldehyde in the felt can be eliminated to target level($0.2{\mu}g$) after introducing 0.5 wt% of NCB into the felt. Detector tube method for analyzing formaldehyde gas was more accurate than HPLC method. Formaldehyde can be eliminated to target level (64 ppb) after introducing 0.5 wt% of NCB into the felt. We also found that TVOC can be reduced to target level ($0.32{\mu}g$) after introducing 2.0 wt% of NCB. Upon introducing small amounts of NCB into the felt, it was possible that the level of formaldehyde, acetaldehyde and TVOC formed from the felts can be reduced to the target level. We also suggest the effective analyzing method of TVOCs.

$TiO_2$/Carbon felt의 광전기 화학반응에 의한 퍼클로레이트 이온 제거

  • Kim, Jong-U;Min, Hyeong-Seop;Ju, Byeong-Gwon;Lee, Jeon-Guk
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.57.2-57.2
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    • 2009
  • 퍼클로레이트 이온($ClO_4^-$)는 자연적으로 혹은 인공적으로 만들어지며 퍼클로릭산이나 암모늄 퍼클로레이트나, 포타슘 퍼클로레이트 혹은 소듐퍼클로레이트 염의 형태로 존재하며, 물에 아주 잘 녹고, 끓여도 제거되지 않으며, 활성 탄소와 같은 광물에도 흡착 되지 않는 성질로 인해, 기존 물리적인 정수 방법으로는 제거하기 어렵다. 또한 우리 몸에 흡수되면, 요오드가 갑상선에 흡수되는 작용을 방해하여 갑상선 기능장애를 초래한다. 이러한 퍼클로레이트 이온의 제거방법으로는 이온교환법이나 생물학적 방법 등이 개발되어져 있으나, 제거 시스템에 이동 및 안전한 농도까지 제거 등의 문제점으로 인한 퍼클로레이트 이온을 환원시키는 촉매 환원 반응에 의한 퍼클로레이트 이온 제거 기술 개발이 필요하다. 이런 촉매 환원에 필요한 수소 환원제를 발생시키기 위해서, 본 연구에서는 Carbon felt 위에 DC magnetron sputtering에 의한 thin film $TiO_2$과 regine을 이용한 powder $TiO_2$ 시편을 제작하였다. 이렇게 제작 된 $TiO_2$/Carbon felt의 미세구조 및 특성은 XRD, SEM, UV-vis-NIR 등을 통하여 분석하였다. UV 조사에 의해 $TiO_2$/Carbon felt 시편의 산소와 수소 발생과 DC bias의 걸어주었을 때 산소와 수소 발생 차이 등을 비교하였고, 이에 따른 퍼클로 레이트 이온의 분해 영향을 알아보았다.

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Reduction of Volatile Organic Compounds Emitted from Automobile Felt by Activated Carbon and Hollow Core/Mesoporous Shell Carbon Ball (자동차용 팰트로부터 방출되는 휘발성 유기화합물의 저감 연구)

  • Park, Seung-Kyu;Kim, Heon-Chang
    • Applied Chemistry for Engineering
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    • v.21 no.6
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    • pp.680-683
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    • 2010
  • Nano carbon balls (NCBs), activated carbons (ACs) and their mixture (new carbon mixtures, NCMs) were used to reduce volatile organic compounds (VOCs) emitted from the automobile felt. The optimum analytical method to measure the trace amount of the VOCs, including formaldehyde and acetaldehyde, has been established by utilizing high performance liquid chromatography (HPLC) and gas chromatography (GC). The levels of formaldehyde and acetaldehyde released from newly produced felt were in the ranges of 0.3~6.0 ppm and 0.2~3.0 ppm, respectively. After 14 days of aging at the room temperature, however, their levels were still in the ranges of 0.2~0.5 ppm and 0.2~0.4 ppm, respectively. By applying NCMs of 2 wt% to the automobile felt, the amount of the total volatile organic compounds (TVOCs) was reduced under the chronic inhalation minimum risk level of $0.32mmmm{\mu}g/TP$.

Effect of surface modification of carbon felts on capacitive deionization for desalination

  • Lee, Jong-Ho;Ahn, Hong-Joo;Cho, Donghwan;Youn, Jeong-Il;Kim, Young-Jig;Oh, Han-Jun
    • Carbon letters
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    • v.16 no.2
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    • pp.93-100
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    • 2015
  • Surface modified carbon felts were utilized as an electrode for the removal of inorganic ions from seawater. The surfaces of the carbon felts were chemically modified by alkaline and acidic solutions, respectively. The potassium hydroxide (KOH) modified carbon felt exhibited high Brunauer-Emmett-Teller (BET) surface areas and large pore volume, and oxygen-containing functional groups were increased during KOH chemical modification. However, the BET surface area significantly decreased by nitric acid ($HNO_3$) chemical modification due to severe chemical dissolution of the pore structure. The capability of electrosorption by an electrical double-layer and the efficiency of capacitive deionization (CDI) thus showed the greatest enhancement by chemical KOH modification due to the appropriate increase of carboxyl and hydroxyl functional groups and the enlargement of the specific surface area.