• 한국수소및신에너지학회논문집
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• 제27권4호
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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.

• 한국수소및신에너지학회논문집
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• 제32권4호
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• pp.256-262
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• 2021

A carbon felt electrode was prepared using ozone and ammonia sequential treatment and applied as an electrode for a vanadium redox flow battery (VRFB). The physical and electrochemical analyses demonstrate that the oxygen groups facilitate nitrogen doping in the carbon felt. Carbon felt (J5O3+NH3), which was subjected to ammonia heat treatment after ozone treatment, showed higher oxygen and nitrogen contents than carbon felt (J5NH3+O3), which was subjected to ammonia heat treatment first and then ozone treatment. From the charging/discharging of VRFB, the J5O3+NH3 carbon felt electrode showed 14.4 Ah/L discharge capacity at a current density of 150 mA /cm², which was 15% and 33% higher than that of J5NH3+O3 and non-activated carbon felt (J5), respectively. These results show that ozone and ammonia sequential treatment is an effective carbon felt activation method to increase the performance of the vanadium redox flow battery.

• 한국수소및신에너지학회논문집
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• 제28권2호
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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.

• 한국수소및신에너지학회논문집
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• 제22권5호
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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.

• 전기화학회지
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• 제12권3호
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• pp.263-270
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• 2009

레독스 흐름 전지의 전극으로 사용하기 위해 탄소펠트를 열처리와 산처리 방법으로 산화 개질하였다. 열중량 분석결과 열처리 또는 산처리에 의하여 탄소펠트의 섬유 표면에 고분자 물질이 제거되고 산소 관능기가 도입된 것을 확인할 수 있었으며 습식 방법인 산처리 방법보다 건식방법인 열처리 방법이 기계적 안정성을 유지하는데 효과적인 처리 방법으로 나타났다. XPS, 원소분석을 통하여 500$^{\circ}C$에서 4시간 열처리한 탄소펠트의 표면에 산소 관능기가 부가된 것을 확인하였으며 질소흡착실험에서 거의 없던 표면적이 96 $m^2/g$로 증가한 것을 알 수 있었다. CV실험 및 분극 실험을 수행한 결과 500$^{\circ}C$ 열처리 전극의 활성화 저항이 가장 낮게 나타났다. 산처리한 탄소펠트와 400$^{\circ}C$, 500$^{\circ}C$에서 열처리한 탄소펠트를 이용하여 바나듐 레독스 흐름 전지를 구성하고 충/방전 실험을 실시한 결과 충/방전 전압효율이 산처리 전극의 경우 86.6%, 400$^{\circ}C$ 열처리 전극의 경우 89.6%, 500$^{\circ}C$ 열처리 전극의 경우 90.6%로 500$^{\circ}C$ 열처리 전극이 가장 우수하였다.

• Korean Chemical Engineering Research
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• 제53권5호
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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.

• Journal of Electrochemical Science and Technology
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• 제14권2호
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• pp.131-138
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• 2023

The carbon felt is usually hired as electrodes for vanadium redox flow battery (VRFB). In the study, surface modification of carbon felt under CO₂ atmosphere with variables of operating various temperature ranges between 700℃ and 900℃. The qualitative and quantitative analysis were carried out such as scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) to observe degree of surface modification. Result of XPS analysis confirmed increase of carbon and oxidation functional group on the surface with increase of temperature. SEM image was discovered similar phenomena. Electrochemical characteristics such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed the improved electrode performance with increase of temperature. However, the electrochemical performance under treatments temperature of 900℃ was less than that of under treatment temperature of 850℃ due to weight loss at the treatment temperature of 900℃. From the CV and EIS results, the best electrochemical characteristics was at the temperature of 850℃. That of at the temperature of 900℃ was decreased due to weight loss. The energy efficiencies (EE) obtained from full cell test were 69.37, 80.76, 82.45, and 75.47%, at the temperature of 700, 800, 850, and 900℃, respectively.

• Journal of Electrochemical Science and Technology
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• 제8권2호
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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.

• 한국응용과학기술학회지
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• 제26권1호
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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.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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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.