• 공업화학
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• 제20권6호
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• pp.700-704
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• 2009

본 연구에서는 다공성 탄소전극의 내부 전해질 농도에 따른 전극의 전기화학적 특성 변화를 연구하였다. 다공성 탄소전극의 내부를 0.01, 0.05, 0.1, 0.5 M KCl 용액으로 채우고 양이온교환막을 결합한 후 cyclic voltammetry, chronoamperometry, impedance spectroscopy 분석을 실시하였다. 실험결과 전극의 특성은 전극 내부의 전해질 농도에 따라 큰 차이를 보였으며 농도가 높을수록 전극 내부의 charging 저항이 감소하여 전기용량이 크게 증가하는 것을 알 수 있었다. 실험결과로부터 이온교환막을 결합한 축전식 탈염공정에서 전극 내부의 전해질 농도를 높임으로써 저 농도의 염수를 효과적으로 탈염할 수 있을 것으로 기대된다.

• 전기화학회지
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• 제10권4호
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• pp.252-256
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• 2007

A series of spherical porous carbons were prepared via resorcinol-formaldehyde (RF) sol-gel polymerization in the presence of cationic surfactant (CTAB, cetyltrimethylammonium bromide), wherein the carbon sphere size was controlled by varying the CTAB introduction time after a pre-determined period of addition reaction (termed as "pre-curing"). The sphere size gradually decreases with an increase in the pre-curing time within the range of 30-150 nm. The carbons possess two types of pores; one inside carbon spheres (intra-particle pores) and the other at the interstitial sites made by carbon spheres (inter-particle pores). Of the two, the surface exposed on the former was dominant to determine the electric double-layer capacitor (EDLC) performance of porous carbons. As the intra-particle pores were generated inside RF gel spheres by gasification, the pore diameter was similar for all these carbons, thereby the pore length turned out to be a decisive factor controlling the EDLC performance. The charge-discharge voltage profiles and complex capacitance analysis consistently illustrate that the smaller-sized RF carbons deliver a better rate capability, which must be the direct result of facilitated ion penetration into shorter pores.

• 한국수소및신에너지학회논문집
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• 제27권2호
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• pp.176-181
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• 2016

Recent years, supercapacitors have been attracting a growing attention as an efficient energy storage, due to their long-lifetime, device reliability, simple device structure and operation mechanism and, most importantly, high power density. Along with the increasing interest in flexible/stretchable electronics, the supercapacitors with compatible mechanical properties have been also required. A eutectic gallium-indium (EGaIn) liquid metal could be a strong candidate as a soft electrode material of the supercapacitors because of its insulating surface oxide layer for electric double layer formation. Here, we report the electrochemical study on the charging/reaction process at the interface of EGaIn liquid metal and electrolyte. Numerical fitting of the charging current curves provides the capacitance of EGaIn/insulating layer/electrolyte (${\sim}38F/m^2$). This value is two orders of magnitude higher than a capacitance of a general metal electrode/electrolyte interface.

• Journal of Electrochemical Science and Technology
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• 제15권2호
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• pp.276-290
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• 2024

A study of the transition from transitory state to steady state in DSSCs based on natural dyes is presented; cochineal was used as dye and Li⁺, Na⁺, and K⁺ were the ions added to the electrolyte. The photocurrent profiles were obtained as a function of time. Several DSSCs were prepared with different cations and their role and the transitory-to-steady transition was determined. A novel hybrid charge carrier source model based on the Heaviside function H(t) and the Lambert-Beer law, was developed and applied to analysis of the transient response of the output photocurrent. Additionally, the maximum effective light absorption coefficient α and the electronic extraction rate κ for each ion were determined: ${\alpha}_{Li^+,Na^+,K^+}\,=\,(0.486,\,0.00085,\,0.1126)\,cm^{-1}$, and also the electronic extraction rate ${\kappa}^{Li^+,Na^+,K^+}_{ext.}\,=\,(1410,\,19.07,\,19.69)\,cm\,s^{-1}$. The impedance model using Fick's second law was developed for carrier recombination to characterize the photocurrent.

• Macromolecular Research
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• 제17권10호
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• pp.746-749
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• 2009

Poly(ethylene terephthalate) (PET) fabric/poly(3,4-ethylenedioxythiophene) (PEDOT) composite with stable and high electrochemical activity was fabricated by chemical and electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) on a PET fabric in sequence. Effects of polymerization conditions on the following characteristics of the composite were studied: electrical conductivity and surface morphology. The electrochemical properties were also investigated by cyclic voltammetry and cyclic charge/discharge experiments. The specific volume resistivity, electrical conductivity and specific discharge capacitance of the composite were 0.034 $\Omega-cm$ and 25 S/cm, and 54.5 F/g, respectively.

• 한국수소및신에너지학회논문집
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• 제18권4호
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• pp.446-451
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• 2007

Physicochemical properties of carbon nanofibers were evaluated as a supercacitor electrode materials could store electrochemical energy reversibly. A capacitance of carbon nanofiber electrode was increased gradually, depending on the PVDF binder ratio. A feasibility of EDLC electrode was estimated with specific surface area measurement by BET method and mesopore structure of carbon nanofiber surface could be explained electrochemical absorption-desorption in aqueous electrolyte. PVDF 5 wt.% ratio in electrode was observed a suitable binder amount by CV result.

• Carbon letters
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• 제15권3호
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• pp.187-191
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• 2014

This study reports on the influence of N-butyl-N-methylpyrrolidinium tetrafluoroborate ($PYR_{14}BF_4$) ionic liquid additive on the conducting and interfacial properties of organic solvent based electrolytes against a carbon electrode. We used the mixture of ethylene carbonate/dimethoxyethane (1:1) as an organic solvent electrolyte and tetraethylammonium tetrafluoroborate ($TEABF_4$) as a common salt. Using the $PYR_{14}BF$ ionic liquid as additive produced higher ionic conductivity in the electrolyte and lower interface resistance between carbon and electrolyte, resulting in improved capacitance. The chemical and electrochemical stability of the electrolyte was measured by ionic conductivity meter and linear sweep voltammetry. The electrochemical analysis between electrolyte and carbon electrode was examined by cyclic voltammetry and electrochemical impedance spectroscopy.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.480.2-480.2
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• 2014

Electrochemical capacitors have been the most strong energy storage devices due to high power density and long cycle stability. Pristine carbon nanotubes are promising electrode materials for excellent electrical conductivity and high specific surface area in electrochemical capacitor. However, the practical application of pristine carbon nanotubes was limited by the aggregation into bundles due to van der Waals force. In this research, we explained how multi-walled carbon nanotubes (MWCNT) functionalized by carboxyl, sulfonic, and amine groups (CNT-COOH, CNT-SO3H, CNT-NH2) to improve the performances of MWCNT. Functionalized CNTs showed two- to four-fold increase in capacitance over that of pristine CNTs, while maintaining reasonable cyclic stability. But, the CNT-COOH showed the lowest rate capability of 57% compared to 84%, 86% of CNT-SO3H and CNT-NH2. As demonstrated by the spectroscopic analysis, This reseach showed how surface functional group of carbon nanotubes change capacitor performances.

• 분석과학
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• 제8권4호
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• pp.663-668
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• 1995

Ion transport of a polypyrrole/chloride (PPy/Cl) film and a polypyrrole/poly(styenesulfonate) (PPy/PSS) film as a function of applied dc potential was investigated by employing electrogravimetric impedance technique and electrochemical impedance technique. The cation and anion contribution to the whole charge capacitance and the diffusion coefficients of cation and anion in a PPy/PSS film were calculated by fitting the electrogravimetric impedance data with proposed model circuit. The diffusion coefficients of $Na^+$ in a 1 M $NaClO_4$ solution are over 1 order of magnitude larger than those of $ClO{_4}^-$, and $ClO{_4}^-$ contribution to charge compensation decreases as dc potential lowers. The charge compensation of a PPy/Cl film ir a 1 M CsCl solution is carried out largely by $Cl^-$ at 0.2 V vs. Ag/AgCl and by $Cs^+$ as well as $Cl^-$ at -0.4 V.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2002년도 추계학술대회
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• pp.273-277
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• 2002

In the electrode fabrication of unit cell, we found that optimal the electrochemical characteristics were obtained with at 90 wt.% of activated carbon(BP-20), 5 wt.% of conducting agent(Ppy, Super P) and 5 wt.% of P(VdF-co-HFP)/PVP mixed binder. The electrochemical characteristics of unit cell with Ppy improver were as follows : 37.6 F/g of specific capacitance, 0.98 $\Omega$ of AC-ESR, 2.92 Wh/kg and 6.05 Wh/L of energy density, and 754 W/kg and 1,562 W/L of power density. It was confirmed that internal resistance were reduced due to the increase of electrical conductivity and filling density by the introduction of conductivity agent, and content of conducting agent was suitable in the range of 4~6 wt.%. According to the impedance measurement of the electrode with conductivity agent, we found that it was possible to charge rapidly by the fast steady-state current convergence due to low equivalent series resistance(AC-ESR), fast charge transfer rate at interface between electrode and electrolyte, and low RC time constant.