• Carbon letters
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• 제4권2호
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• pp.64-68
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• 2003

A study on the electrosorption of uranium ions onto a porous activated carbon fiber (ACF) was performed to treat uraniumcontaining lagoon sludge. The result of the continuous flow-through cell electrosorption experiments showed that the applied negative potential increased the adsorption kinetics and capacity in comparison to the open-circuit potential (OCP) adsorption for uranium ions. Effective U(VI) removal is accomplished when a negative potential is applied to the activated carbon fiber (ACF) electrode. For a feed concentration of 100 mg/L, the concentration of U(VI) in the cell effluent is reduced to less than 1 mg/L. The selective removal of uranium ions from electrolyte was possible by the electrosorption process.

• Carbon letters
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• 제3권1호
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• pp.6-12
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• 2002

A study on the electrosorption of $Co^{2+}$ and $Sr^{2+}$ ions onto a porous activated carbon fiber (ACF) was performed to treat radioactive liquid wastes resulting from chemical or electrochemical decontamination and to regenerate the spent carbon electrode. The result of batch electrosorption experiments showed that applied negative potential increased adsorption kinetics and capacity in comparison with open-circuit potential (OCP) adsorption for $Co^{2+}$ and $Sr^{2+}$ ions. The adsorbed $Co^{2+}$ and $Sr^{2+}$ ions are released from the carbon fiber by applying a positive potential on the electrode, showing the reversibility of the sorption process. The possibility of application of the electrosorption technique to the separation of radionuclides was examined. The result of a selective removal experiments of a single component from a mixed solution showed that perfect separation of $Co^{2+}$ and $Sr^{2+}$ ions was possible by the electrosorption process.

• 대한환경공학회지
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• 제35권10호
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• pp.749-755
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• 2013

본 연구의 목적은 분진제거를 목적으로 제작된 활성탄 전극의 적정 간격 및 적정 전압 그리고 분진 제거효율을 통하여 전극의 적정한 배열에 대하여 알아보고자 수행하였다. 여러 전극 간격 별로 수행한 실험결과로부터 분진의 부착 및 탈착의 빈도수는 전극의 간격이 가까워질수록 증가하였다. 전극 단위면적 당 분진 부착량은 전극간격이 멀어질수록 증가하였지만 총 부착량에 있어서는 전극간격이 가까울수록 전극의 설치수가 많아져서 증가하였다. 이와같은 실험결과로부터 분진제거 챔버에서 전극의 설치간격은 앞단의 경우는 분진 부하량이 높기 때문에 제거량이 많도록 전극의 간격을 멀리하고 후단은 제거효율을 높이기 위하여 전극간격을 가깝게 설치하는 것이 바람직하다고 사료되었다. 그리고 전압 5 kV, 전극간격 2 cm에서 전압의 변화에 따른 분진부착량 실험결과에서 전압의 변화와 부착량과는 상관관계가 없었다.

• Carbon letters
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• 제15권1호
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• pp.71-76
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• 2014

Activated carbon nanofibers (ACNF) were prepared from polyacrylonitrile (PAN)-based nanofibers using $CO_2$ activation methods with varying activation process times. The surface and structural characteristics of the ACNF were observed by scanning electron microscopy and X-ray diffraction, respectively. $N_2$ adsorption isotherm characteristics at 77 K were confirmed by Brunauer-Emmett-Teller and Dubinin-Radushkevich equations. As experimental results, many holes or cavernous structures were found on the fiber surfaces after the $CO_2$ activation as confirmed by scanning electron microscopy analysis. Specific surface areas and pore volumes of the prepared ACNFs were enhanced within a range of 10 to 30 min of activation times. Performance of the porous PAN-based nanofibers as an electrode for electrical double layer capacitors was evaluated in terms of the activation conditions.

• Journal of Electrochemical Science and Technology
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• 제2권2호
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• pp.63-67
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• 2011

To examine the effects of a two-cation ionic liquid as an electrolyte component of a supercapacitor, 1,4-bis(3-methylimidazolium-1-yl)butane tetrafluoroborate ($MIBBF_4$), dissolved in propylene carbonate (PC) or acetonitrile (ACN), is newly synthesized and tested here for potential use as an electrolyte of capacitor. The $MIBBF_4$ salt exhibits higher ionic conductivity in ACN than in PC. The supercapacitive properties of capacitors containing an activated carbon electrode and various electrolytes are evaluated using cyclic voltammetry and electrochemical impedance spectroscopy. The capacitor adopting the $MIBBF_4$/ACN electrolyte shows the largest specific capacitance at low scan rates, whereas the capacitor adopting the 1-ethyl-3-methylimidazolium tetrafluoroborate $(EMIBF_4)$/ACN electrolyte shows the largest specific capacitance at high scan rates.

• Journal of Electrochemical Science and Technology
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• 제14권3호
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• pp.222-230
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• 2023

Capacitive deionization of saline water is one of the most promising water purification technologies due to its high energy efficiency and cost-effectiveness. This study synthesizes porous carbon composites composed of reduced graphene oxide (rGO) and activated carbon (AC) with various rGO/AC ratios using a facile chemical method. Surface characterization of the rGO/AC composites shows a successful chemical reduction of GO to rGO and incorporation of AC into rGO. The optimized rGO/AC composite electrode exhibits a specific capacitance of ~243 F g^-1 in a 1 M NaCl solution. The galvanostatic charging-discharging test shows excellent reversible cycles, with a slight shortening in the cycle time from the ~260^th to the 530^th cycle. Various monovalent sodium salts (NaF, NaCl, NaBr, and NaI) and chloride salts (LiCl, NaCl, KCl, and CsCl) are deionized with the rGO/AC electrode pairs at a cell voltage of 1.3 V. Among them, NaI shows the highest specific adsorption capacity of ~22.2 mg g^-1. Detailed surface characterization and electrochemical analyses are conducted.

• Bulletin of the Korean Chemical Society
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• 제31권11호
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• pp.3183-3189
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• 2010

In order to increase the specific capacitance and energy density of supercapacitors, non-aqueous supercapacitors were prepared using lithium transition-metal oxides and activated carbons as active materials. The electrochemical properties were analyzed in terms of the content of lithium transition-metal oxides. The results of cyclic voltammetry and AC-impedance analyses showed that the pseudocapacitance may stem from the synergistic contributions of capacitive and faradic effects; the former is due to the electric double layer which is prepared in the interface of activated carbon and organic electrolyte, and the latter is due to the intercalation of lithium ($Li^+$) ions. The specific capacitance and energy density of a supercapacitor improved as the lithium transition-metal oxides content increased, showing 60% increase compared to those of supercapacitor using a pure activated carbon positive electrode.

• Carbon letters
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• 제16권2호
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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.

• 한국전기전자재료학회논문지
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• 제19권9호
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• pp.849-854
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• 2006

In this study, the hybrid electrodes, composed of the activated carbon powders and $LiCoO_{2}$ powders, were prepared as a cathode for the high-capacitance type hybrid capacitor, and the electrochemical properties of the hybrid electrodes were examined in terms of the weight composition and the milling time of $LiCoO_{2}$ powders. The specific volumetric capacities were increased with increasing of the composition of $LiCoO_{2}$ powders in the hybrid electrodes. On the other hand the coin cell capacitors, using the hybrid electrodes with $LiCoO_{2}$ poweders milled for 200 h, have exhibited the lower internal resistivities and the better capacity retention after 100 charge-discharge cycle than those of the coin cell capacitors using the hybrid electrodes with raw $LiCoO_{2}$ powders.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.581-584
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• 2001

For the first time, a totally solid state electric double layer capacitor has been fabricated using an alkaline polymer electrolyte and an activated carbon powder as electrode material. The polymer electrolyte serves both as separator as well as electrode binder. The capacitor has a three-layer structure; electrode-electrolyte-electrode. A cyclic voltammetry and constant current discharge have been used for the determination of the electro chemical performance of capacitors.