• Korean Journal of Acupuncture
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• v.31 no.2
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• pp.90-97
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• 2014

Objective : The objective of this study is to investigate the effects of smoking on the skin bioelectrical capacitance at specific acupoints of lung meridian. Methods : Bioelectrical capacitance was measured on bilateral six source points(bilateral LU10, LU9, LU7, LU6, LU5, LU1), and the changes with time and between left and right side were analyzed. Results : The skin bioelectrical capacitance at specific acupoints of lung meridian was significantly increased after smoking. And it recovered as time passed. The change of the skin bioelectrical capacitances at specific acupoints of lung meridian with time were similar between left and right. Conclusion : Smoking increases the bioelectrical capacitance at specific acupoints of lung meridian. There is no difference between the effects of smoking on the bioelectrical capacitance at left and right specific acupoints of lung meridian.

• Proceedings of the Safety Management and Science Conference
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• 2003.11a
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• pp.343-350
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• 2003

The best Ppy weight ratio was 7 wt% and the optimal electrode composition ratio was 78 : 17 : 5 wt.% of (MSP-20 : BP-20 =1 : 1), (Super P : Ppy =10 : 7) and P(VdF-co-HFP). Implantation of Ppy as the conducting agents have led to superior electrochemical characteristics because of the low of internal resistance and faradaic capacitance. The result of unit cell with Ppy 7 wt% were as follows: 28.02 Fig of specific capacitance, 1.34 Ω of DC-ESR and 0.36 Ω of AC-ESR. Unit cell showed a good stability up to 200 charge-discharge cycles, retaining 82% of their original capacity at 200 cycles. From the analysis of impedance, the electrodes with Ppy 7 wt% showed low ESR, low charge transfer resistance and quick reaction rate. It was inferred that quick charge-discharge was possible. As compared with the specific capacitance (rectangular shape) of CV, it was also concluded that the specific capacitance originated from thecompound phenomena of the faradaic capacitance by oxidation and reduction of Ppy and the non-faradaic capacitance by adsorption-desorption of activated carbon.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.2
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• pp.112-116
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• 2018

Electric double layer capacitors (EDLCs) are promising candidates for energy storage devices in electronic applications. An EDLC yields high power density but has low specific capacitance. Carbon material is used in EDLCs owing to its large specific surface area, large pore volume, and good mechanical stability. Consequently, the use of carbon materials for EDLC electrodes has attracted considerable research interest. In this paper, in order to evaluate the electrochemical performance, graphene is used as an EDLC electrode with flake sizes of 3, 12, and 60 nm. The surface characteristic and electrochemical properties of graphene were investigated using SEM, BET, and cyclic voltammetry. The specific capacitance of the graphene based EDLC was measured in a 1 M $TEABF_4/ACN$ electrolyte at the scan rates of 2, 10, and 50 mV/s. The 3 nm graphene electrode had the highest specific capacitance (68.9 F/g) compared to other samples. This result was attributed to graphene's large surface area and meso-pore volume. Therefore, large surface area and meso-pore volume effectively enhances the specific capacitance of EDLCs.

• Journal of Electrochemical Science and Technology
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• v.12 no.3
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• pp.339-345
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• 2021

Spent activated carbons (SACs) collected from a water treatment plant were regenerated and then adopted as electrochemical material in capacitors. The SACs used in this study were regenerated via two steps, namely thermal and chemical activation. However, during the activation process, the adsorbates were converted into ashes, which caused pore blockage and decreased specific surface area. The regenerated SACs were washed with acid solutions with different levels of acidity (strong: HCl, mild: H₃PO₄, and weak: H₂O₂) to remove the ashes. The regenerated SACs washed with HCl exhibited the highest specific surface area, although their capacitance was not the highest. Conversely, the specific surface area of regenerated SACs washed using H₃PO₄ was slightly lower than that of HCl, but exhibited higher capacitance and electrochemical stability. Although the strong acid removed the generated ashes in the pores efficiently, it could adversely affect their structural stability, which would lead to lower capacitance.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.214.2-214.2
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• 2011

In this work, porous carbon based electrodes are prepared by carbonization using poly(vinylidene fluoride) (PVDF)/carbon nanotube (CNT) composites to further increase the specific capacitance for supercapacitors. Electrode materials investigate the aspects of specific capacitance, pore size distribution and surface area: influence of carbonization temperatures of PVDF/CNT composites. The electrochemical properties are investigated by cyclic voltammetry, impedance spectra, and galvanostatic charge-discharge performance with in $TEABF_4$ (tetraethylammonium tetrafluoroborate)/acetonitrile as non-aqueous electrolyte. From the results, the highest value of specific capacitance of ~101 $F{\cdot}g^{-1}$ is obtained for the samples carbonized at $600^{\circ}C$. Furthermore, pore size of samples control be low 7 nm through carbonization process. It is suggested that micropores significantly contribute to the specific capacitance, resulting from improved charge transfer.

• Carbon letters
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• v.16 no.2
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• pp.78-85
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• 2015

Activated carbons (ACs) were prepared by activation of coal tar pitch (CTP) in the range of $700^{\circ}C-1000^{\circ}C$ for 1-4 h using potassium hydroxide (KOH) powder as the activation agent. The optimal activation conditions were determined to be a CTP/KOH ratio of 1:4, activation temperature of $900^{\circ}C$, and activation time of 3 h. The obtained ACs showed increased pore size distribution in the range of 1 to 2 nm and the highest specific capacitance of 122 F/g in a two-electrode system with an organic electrolyte, as measured by a charge-discharge method in the voltage range of 0-2.7 V. In order to improve the performance of the electric double-layer capacitor electrode, various mixtures of CTP and petroleum pitch (PP) were activated at the optimal activation conditions previously determined for CTP. Although the specific capacitance of AC electrodes prepared from CTP only and the mixtures of CTP and PP was not significantly different at a current density of 1 A/g, the AC electrodes from CTP and PP mixtures showed outstanding specific capacitance at higher current rates. In particular, CTP-PP61 (6:1 mixture) had the highest specific capacitance of 132 F/g, and the specific capacitance remained above 90% at a high current density of 3 A/g. It was found that the high specific capacitance could be attributed to the increased micro-pore volume of ACs with pore sizes from 1 to 2 nm, and the high power density could be attributed to the increased meso-pore volume.

• Carbon letters
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• v.25
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• pp.14-24
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• 2018

Electrochemical properties and performance of composites performed by incorporating metal oxide or metal hydroxide on carbon materials based on graphene and carbon nanotube (CNT) were analyzed. From the surface analysis by field emission scanning electron microscopy and field emission transmission electron microscopy, it was confirmed that graphene, CNT and metal materials are well dispersed in the ternary composites. In addition, structural and elemental analyses of the composite were conducted. The electrochemical characteristics of the ternary composites were analyzed by cyclic voltammetry, galvanostatic charge-discharge tests, and electrochemical impedance spectroscopy in 6 M KOH, or $1M\;Na_2SO_4$ electrolyte solution. The highest specific capacitance was $1622F\;g^{-1}$ obtained for NiCo-containing graphene with NiCo ratio of 2 to 1 (GNiCo 2:1) and the GNS/single-walled carbon $nanotubes/Ni(OH)_2$ (20 wt%) composite had the maximum specific capacitance of $1149F\;g^{-1}$. The specific capacitance and rate-capability of the $CNT/MnO_2/reduced$ graphene oxide (RGO) composites were improved as compared to the $MnO_2/RGO$ composites without CNTs. The $MnO_2/RGO$ composite containing 20 wt% CNT with reference to RGO exhibited the best specific capacitance of $208.9F\;g^{-1}$ at a current density of $0.5A\;g^{-1}$ and 77.2% capacitance retention at a current density of $10A\;g^{-1}$.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.822-827
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• 1999

The specific capacitance characteristics which were of the electric double layer capacitors(ELDC) made of phenol based activated carbon fiber(ACF) electrodes and organic electrolytes has been investigated with respect to different specific surface area of electrodes and different kinds of organic electrolytes. Throughout charge-discharge cell tests, it has been found that larger surface area and larger pore diameter of electrodes contribute to increase the specific capacitance. Binary mixture of organic solvent with propylene cabonate(PC) and tetrahydrofuran(THF) for 1 M-$LiClO_4$ electrolyte has a higher specific capacitance than single solvent of PC or mixed solvent with PC and diethyl cabonate(DEC). Also, even though 1 M-tetraethylamonium perchlorate(TEAPC) of organic electrolyte shows higher specific capacitance, it has longer charge time because of its lower ion mobility.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.597-597
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• 2012

A simple solution-based method is developed to deposit crystalline ultrathin (2 nm) nickel hydroxide on vertically grown ZnO nanowires to achieve high specific capacitance and long-term life for flexible and wearable energy storage devices. Ultrathin crystalline $Ni(OH)_2$ enables fast and reversible redox reaction to improve the specific capacitance by utilizing maximum number of active sites for the redox reaction while vertically grown ZnO nanowires on wearable textile fiber effectively transport electrolytes and shorten the ion diffusion path. Under the highly flexible state $Ni(OH)_2$ coated ZnO nanowires electrode shows a high specific capacitance of 2150 F/g (based on pristine $Ni(OH)_2$ in 1 M LiOH aqueous solution with negligible decrease in specific capacitance after 1000 cycles. The synthesized energy-storage electrodes are easy-to-assemble which can provide unprecedented design ingenuity for a variety of wearable and flexible electronic devices.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.69-70
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• 2003

10 wt.% of PAN was dissolved in N,N-dimethylformamide (DMF) and 1 wt. % of the multi wall carbon nanotubes (MWCNTs) was evenly dispersed in PAN solution by using ultrasonic miner. The 1 wt.% addition of MWCNT increased the specific capacitance by two times more from 82 to 160 F/g. The specific capacitance of carbon nanofiber(CNF)/carbon nanotube(CNT) composite capacitors was about 90 F/g at the current density of 500 mA/g. This value is even larger than the capacitance from the CNF electrode at the current density of 5 mA. The relatively high capacitance at the high current density is a practical importance for applications to supercapacitor in motor vehicle.