• 대한임상전기생리학회지
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• 제10권2호
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• pp.37-42
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• 2012

Purpose : This study is to examine the effect of electrode size during transcranial direct current stimulation on hand function. Methods : By randomly assigning 26 right hand dominant subjects to two groups (I: carbon rubber electrode / II: disposable circular self-adhesive electrodes) with 13 subjects in each group depending on the electrode size, a positive electrodeof transcranial direct current stimulation was placed on the primary motor area (C4) and a negative electrode was placed on the left primary motor area (C3) and the stimulation was applied for 20 minutes.Hand function assessment before and after transcranial direct current stimulation were measured with JTT (Jebsen-Taylor hand function test). Results : According to hand function assessment by JTT, there were no interactions on both hands, and statistically significant differences according to time appeared in the main effect test. Conclusion : Regardless of the electrode size, it appears that transcranial direct current stimulation on the primary motor area activated hand function affected.

• Carbon letters
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• 제11권1호
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• pp.38-40
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• 2010

Carbon supported electrocatalysts are commonly used as electrode materials for polymer electrolyte membrane fuel cells(PEMFCs). These kinds of electrocatalysts provide large surface area and sufficient electrical conductivity. The support of typical PEM fuel cell catalysts has been a traditional conductive type of carbon black. However, even though the carbon particles conduct electrons, there is still significant portion of Pt that is isolated from the external circuit and the PEM, resulting in a low Pt utilization. Herein, new types of carbon materials to effectively utilize the Pt catalyst are being evaluated. Carbon nanofiber/activated carbon fiber (CNF/ACF) composite with multifunctional surfaces were prepared through catalytic growth of CNFs on ACFs. Nickel nitrate was used as a precursor of the catalyst to synthesize carbon nanofibers(CNFs). CNFs were synthesized by pyrolysising $CH_4$ using catalysts dispersed in acetone and ACF(activated carbon fiber). The as-prepared samples were characterized with transmission electron microscopy(TEM), scanning electron microscopy(SEM). In TEM image, carbon nanofibers were synthesized on the ACF to form a three-dimensional network. Pt/CNF/ACF was employed as a catalyst for PEMFC. As the ratio of prepared catalyst to commercial catalyst was changed from 0 to 50%, the performance of the mixture of 30 wt% of Pt/CNF/ACF and 70wt% of Pt/C commercial catalyst showed better perfromance than that of 100% commercial catalyst. The unique structure of CNF can supply the significant site for the stabilization of Pt particles. CNF/ACF is expected to be promising support to improve the performance in PEMFC.

• 공업화학
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• 제31권6호
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• pp.639-645
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• 2020

레독스흐름전지(redox flow battery, RFB)의 구성 부품 중 전극은 전해액의 확산층 역할을 함과 동시에 전자의 통로 역할을 담당하여 출력에 직접적인 영향을 미치는 주요 부품이다. 본 연구는 Fe2+/Fe3+와 V2+/V3+를 레독스 커플로 사용한 RFB 시스템에 chloric/sulfuric mixed acid 지지 전해액을 사용한 경우 전극 종류 및 활성화 정도에 따른 용량, 쿨롱 효율, 에너지 효율을 비교하여 최적의 전극 및 활성화 정도를 제시하였다. 실험에 사용된 5종의 탄소 전극을 사용한 단일셀 평가에서 모두 이론 용량에 근사한 값을 보여 신뢰성을 확보하였으며, 사용된 전극 중 GFD4EA는 상대적으로 우수한 에너지 효율 및 충방전 용량을 나타내었다. 활성화 온도에 따른 전기화학적 성능 고찰을 위하여 GFD4EA 전극을 공기 분위기 하에서 400, 450, 500, 600 및 700 ℃에서 열처리하여 활성화하였다. 질량 변화, 주사전자현미경(SEM) 및 XPS 분석을 통하여 활성화 전 후의 물성 변화를 관찰하였으며, 각각의 온도에서 활성화된 전극을 적용한 RFB 단일셀 평가를 실시하여 전기화학적 성능을 비교하였다.

• Bulletin of the Korean Chemical Society
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• 제33권5호
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• pp.1523-1526
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• 2012

In this work, we prepared activated multi-walled carbon nanotubes/polyacrylonitrile (A-MWCNTs/C) composites by film casting and activation method. Electrochemical properties of the composites were investigated in terms of serving as MWCNTs-based electrode materials for electric double layer capacitors (EDLCs). As a result, the A-MWCNTs/C composites had much higher BET specific surface area, and pore volume, and lower volume ratio of micropores than those of pristine MWCNTs/PAN ones. Furthermore, some functional groups were added on the surface of the A-MWCNTs/C composites. The specific capacitance of the A-MWCNTs/C composites was more than 4.5 times that of the pristine ones at 0.1 V discharging voltage owing to the changes of the structure and surface characteristics of the MWCNTs by activation process.

• 한국재료학회지
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• 제32권2호
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• pp.107-113
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• 2022

Fibrous supercapacitors (FSs), owing to their high power density, good safety characteristic, and high flexibility, have recently been in the spotlight as energy storage devices for wearable electronics. However, despite these advantages, FCs face many challenges related to their active material of carbon fiber (CF). CF has low surface area and poor wettability between electrode and electrolyte, which result in low capacitance and poor long-term stability at high current densities. To overcome these limits, fibrous supercapacitors made using surface-activated CF (FS-SACF) are here suggested; these materials have improved specific surface area and better wettability, obtained by introducing porous structure and oxygen-containing functional groups on the CF surface, respectively, through surface engineering. The FS-SACF shows an improved ion diffusion coefficient and better electrochemical performance, including high specific capacity of 223.6 mF cm^-2 at current density of 10 ㎂ cm^-2, high-rate performance of 171.2 mF cm^-2 at current density of 50.0 ㎂ cm^-2, and remarkable, ultrafast cycling stability (96.2 % after 1,000 cycles at current density of 250.0 ㎂ cm^-2). The excellent electrochemical performance is definitely due to the effects of surface functionalization on CF, leading to improved specific surface area and superior ion diffusion capability.

• 접착 및 계면
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• 제22권1호
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• pp.1-7
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• 2021

신재생 에너지 발전을 통한 안정적인 전력 공급을 위해 대용량 에너지 저장 장치의 중요성이 최근 부각되고 있다. 이러한 관점에서 차세대 이차 전지인 Na-air battery (NAB)는 풍부하고 저렴한 원재료를 통해 대용량을 구현할 수 있어 많은 관심을 받고 있다. 본 연구에서는 Hybrid type Na-air battery를 위한 활성탄 기반 촉매들을 제조하여 이들의 특성을 비교 분석하였다. 특히, 자원 재활용의 관점에서 버려진 오렌지 껍질을 사용하여 활성탄(Orange-C)과 이를 질소를 이용하여 도핑한 활성탄(N-doped-Carbon, Nd-C)을 제조하였으며, 널리 사용되고 있는 Vulcan카본과 성능을 비교하였다. 또한, 제조한 활성탄(Nd-C)이 지지 촉매로 활용 가능한지 확인하기 위해 수정된 폴리올법을 사용하여 Pt/C 촉매(homemade-Pt/C, HM-Pt/C)를 합성하였으며, 상용화된 Pt/C 촉매(Commercial Pt/C)와 전기화학적 성능을 비교하였다. 제조된 Orange-C와 Nd-C는 전형적인 H3 타입 BET isotherm을 보였으며, 이는 마이크로 기공과 메조기공이 존재한다는 증거이다. 또한, HM-Pt/C의 경우, 활성탄(Nd-C) 지지 촉매 위에 Pt 입자가 고르게 분포하고 있음을 TEM 분석을 통해 확인할 수 있었다. 특히, HM-Pt/C 기반의 NAB의 경우, 1st galvanostatic charge-discharge 시험에서 가장 작은 Voltage gap (0.224V)과 우수한 Voltage efficiency (92.34%)를 보였다. 또한, 20사이클 동안 진행한 사이클 성능 시험에서도 가장 안정적인 성능을 보였다.

• Advances in materials Research
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• 제8권1호
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• pp.37-46
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• 2019

Electrochemical double layer capacitors (EDLCs) which are fabricated using carbon based electrodes have been emerging at an alarming rate to fulfill the energy demand in the present day world. Activated charcoal has been accepted as a very suitable candidate for electrodes but its cost is higher than natural graphite. Present study is about fabrication of EDLCs using composite electrodes with activated charcoal and Sri Lankan natural graphite as well as a gel polymer electrolyte which is identified as a suitable substitute for liquid electrolytes. Electrochemical Impedance Spectroscopy, Cyclic Voltammetry and Galvanostatic Charge Discharge test were done to evaluate the performance of the fabricated EDLCs. Amount of activated charcoal and natural graphite plays a noticeable role on the capacity. 50 graphite : 40 AC : 10 PVdF showed the optimum single electrode specific capacity value of 15 F/g. Capacity is determined by the cycling rate as well as the potential window within which cycling is being done. Continuous cycling resulted an average single electrode specific capacity variation of 48 F/g - 16 F/g. Capacity fading was higher at the beginning. Later, it dropped noticeably. Initial discharge capacity drop under Galvanostatic Charge Discharge test was slightly fast but reached near stable upon continuous charge discharge process. It can be concluded that initially some agitation is required to reach the maturity. However, the results can be considered as encouraging to initiate studies on EDLCs using Sri Lankan natural graphite.

• Carbon letters
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• 제15권1호
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• pp.1-14
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• 2014

Carbon nanofibers (CNFs) with diameters in the submicron and nanometer range exhibit high specific surface area, hierarchically porous structure, flexibility, and super strength which allow them to be used in the electrode materials of energy storage devices, and as hybrid-type filler in carbon fiber reinforced plastics and bone tissue scaffold. Unlike catalytic synthesis and other methods, electrospinning of various polymeric precursors followed by stabilization and carbonization has become a straightforward and convenient way to fabricate continuous CNFs. This paper is a comprehensive and brief review on the latest advances made in the development of electrospun CNFs with major focus on the promising applications accomplished by appropriately regulating the microstructural, mechanical, and electrical properties of as-spun CNFs. Additionally, the article describes the various strategies to make a variety of carbon CNFs for energy conversion and storage, catalysis, sensor, adsorption/separation, and biomedical applications. It is envisioned that electrospun CNFs will be the key materials of green science and technology through close collaborations with carbon fibers and carbon nanotubes.

• 공업화학
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• 제10권6호
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• pp.822-827
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• 1999

본 연구에서는 에너지 밀도가 큰 초고용량 캐패시터를 제작하기 위한 기초 연구로서 활성탄소섬유의 물성과 유기 전해질의 특성이 초고용량 캐패시터의 전기화학적 특성에 미치는 영향을 조사하였다. 유기성 전해질의 경우는 이온의 크기가 수용성 전해질 보다 훨씬 크기 때문에 탄소전극의 세공크기에 많은 영향을 받으며, 용량을 발현할 수 있는 유효세공의 크기가 커야 한다는 것을 알 수 있었다. 혼합용매를 이용한 전해액의 조성은 큰 비축전용량과 빠른 충전속도, 그리고 낮은 ESR 및 방전전류의 세기에 대한 높은 비축전용량 유지성 등의 우수한 충방전 특성을 나타내는 것을 알 수 있었고, 전해질의 높은 이온전도도가 용량발현 및 자가방전 특성에 큰기여를 하고 있으며, 전해질 이온의 크기는 충전속도에 많은 영향을 미치는 것을 알 수 있었다.

• Composites Research
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• 제32권5호
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• pp.296-300
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• 2019

2D 전이금속 탄화물(MXenes) 가운데, 타이타늄 기반의 $Ti_3C_2$는 뛰어난 전기전도성과 전기화학적 특성 및 표면작용기의 영향으로 이차 전지와 슈퍼캐패시터와 같은 에너지저장장치의 유망한 전극 물질로 각광받고 있다. 전극으로서 $Ti_3C_2$의 사용은 이온이 반응할 수 있는 표면적을 넓혀줄 뿐만 아니라, 이온의 확산 거리를 줄여주고, 전하의 운동을 향상시켜준다. 이 연구에서, 효율적으로 MAX phase로부터 $Ti_3C_2$를 합성하는 방법을 통해 리튬이온배터리에서 MXene기반의 전극 물질을 위한 새로운 방향을 제시하고자 한다.