• 한국수소및신에너지학회논문집
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• 제21권6호
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• pp.507-512
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• 2010

The effect of catholyte to anolyte amount ratio on the electrodialysis cell performance for HI concentration was investigated. For this purpose, the electrodialysis cell was assembled with Nafion 117 as PEM membrane and activated carbon fiber cloth as electrodes. The initial amount of catholyte was 310 g and that of anolyte varied from 1 to 3 of amount ratio. The calculated electro motive force (EMF) increased with time and the increment enhanced as the amount ratio of catholyte to anolyte decreased. The mole ratios of HI to $H_2O$ (HI molarity) in catholyte were almost the same and exceeded pseudo-azeotropic composition for all amount ratios after 2 h operation. The HI molarity continuously increased with time for 10 h operation. The mole ratio of $I_2$ to HI decreased in catholyte but increased in anolyte. The increment of mole ratio of $I_2$ to HI in anolyte rose as the amount ratio of catholyte to anolyte decreased. In case of 1:1 amount ratio, the cell operation was stopped for the safety at approximately 6 h operation, since the mole ratio of $I_2$ to HI reached solubility limit. The cell voltage of the electrodialysis cell increased with time and the rate of increase was high at low amount ratio. This suggests that the amount ratio of catholyte to anolyte not only crucially influences the cell voltage, but also cell operation condition.

• KEPCO Journal on Electric Power and Energy
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• 제8권2호
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• pp.181-187
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• 2022

As the charges/discharges of VRFB-ESS were repeated during 150cycles or more, the capacity of electrolyte in VRFB-ESS was decreased little by little. It results from the decreasing of the level of anolyte and the increasing of the valance value of the catholyte. Then, we tried to recover the capacity loss with 3 different ways. The first way was that the levels of anolyte and catholyte were allowed to be evenly equalized when the difference in the levels of two different electrolytes were severe. The second one was to lessen the valance value of the catholyte through the reduction reaction to 4-valant ions of 5-valant ions in the catholyte with the reductant, oxalic acid. The last one was that the all electrolytes of analyte and catholyte were allowed to be electro-chemically reduced to 3.5 of the valance value by oxidizing new electrolyte with 3.5 valance ions. The last way was the most effective to recover the capacity loss.

• Journal of Electrochemical Science and Technology
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• 제13권2호
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• pp.308-320
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• 2022

The high internal resistance (R_int) that develops across the sediment microbial fuel cells (SMFC) limits their power production (~4/10 mW m^-2) that can be recovered from an initial oil-contaminated sediment (OCS). In the anolyte, R_int is related to poor biodegradation activity, quality and quantity of contaminant content in the sediment and anode material. While on the catholyte, R_int depends on the properties of the catholyte, the oxygen reduction reaction (ORR), and the cathode material. In this work, the main factors limiting the power output of the SMFC have been minimized. The power output of the SMFC was increased (47 times from its initial value, ~4 mW m^-2) minimizing the SMFC R_int (28 times from its initial value, 5000 ohms), following the main modifications. Anolyte: the initial OCS was amended with several amounts of gasoline and kerosene. The best anaerobic microbial activity of indigenous populations was better adapted (without more culture media) to 3 g of kerosene. Catholyte: ORR was catalyzed in birnessite/carbon fabric (CF)-cathode at pH 2, 0.8M Na₂SO₄. At the class level, the main microbial groups (Gammaproteobacteria, Coriobacteriia, Actinobacteria, Alphaproteobacteria) with electroactive members were found at C-anode and were associated with the high-power densities obtained. Gasoline is more difficult to biodegrade than kerosene. However, in both cases, SMFC biodegradation activity and power output are increased when ORR is performed on birnessite/CF in 0.8 M Na₂SO₄ at pH 2. The work discussed here can focus on bioremediation (in heavy OCS) or energy production in future work.

• 공업화학
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• 제22권1호
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• pp.67-71
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• 2011

$Li/SO_2Cl_2$ 전지의 양극활물질은 $SO_2Cl_2$인데 이 물질은 전해액의 용매이기도 하다. 이를 일컬어 catholyte (cathode와 electrolyte의 합성어)라 칭하는데 전지의 방전이 진행됨에 따라 소진된다. 따라서 전지 제작 시 투입되는 $SO_2Cl_2$의 특성은 전지의 용량을 결정하는 중요 변수이다. 또한, $Li/SO_2Cl_2$ 전지의 transition minimum voltage (TMV)와 전압지연 편차는 전해액과 리튬의 반응에 의하여 형성된 부동화 막과 관련되는데 이 부동화 막은 전해액 내 불순물(수분 또는 중금속 이온)이 있을 경우 이의 성장이 촉진된다. 따라서 전해액을 정제시키는 기술과 이를 평가하는 방법의 정립은 반드시 필요하다. 본 연구에서는 $LiAlCl_4/SO_2Cl_2$전해액을 $AlCl_3$와 LiCl을 이용하여 제조하였고 제조된 전해액을 이온전도도계와 색도계 및 FT-IR을 이용하여 농도와 수분, 금속함량 등을 평가하였다.

• Journal of Electrochemical Science and Technology
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• 제8권3호
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• pp.236-243
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• 2017

A fixed-bed zinc/nickel redox flow battery (RFB) is designed and developed. The proposed cell has been established in the form of a fixed bed RFB. The zinc electrode is immersed in an aqueous NaOH solution (anolyte solution) and the nickel electrode is immersed in the catholyte solution which is a mixture of potassium ferrocyanide, potassium ferricyanide and sodium hydroxide as the supporting electrolyte. In the present work, the electrode area has been maximized to $1500cm^2$ to enforce an increase in the energy efficiency up to 77.02% at a current density $0.06mA/cm^2$ using a flow rate $35cm^3/s$, a concentration of the anolyte solution is $1.5mol\;L^{-1}$ NaOH and the catholyte solution is $1.5mol\;L^{-1}$ NaOH as a supporting electrolyte mixed with $0.2mol\;L^{-1}$ equimolar of potassium ferrocyanide and potassium ferricyanide. The outlined results from this study are described on the basis of battery performance with respect to the current density, velocity in different electrolytes conditions, energy efficiency, voltage efficiency and power of the battery.

• Environmental Engineering Research
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• 제24권3호
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• pp.456-462
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• 2019

Hydrocarbon contamination is among the most challenging problems in soil remediation. Electrokinetic method can be a promising method to remediate hydrocarbon-contaminated soils. Electrokinetic method consists of different transport phenomena including electro-migration, electrophoresis, and electroosmotic flow. Electroosmotic flow is the main transport phenomenon for hydrocarbon removal in soil porous media. However, the main component of hydrocarbons is the hydrophobic organic which indicates low water solubility; therefore, it makes the electroosmotic flow less effective. The objective of the present study is to enhance electrokinetic remediation of diesel-contaminated silty sand by increasing the solubility of the hydrocarbons in the soil and then increase the efficiency. For this purpose, sodium dodecyl sulfate (SDS) was used as a catholyte. In this content, SDS 0.05 M was used as catholyte and $Na_2SO_4$ 0.1 M was used as an anolyte. Low (1 V/cm) and high (2 V/cm) voltage gradients were used in periodic and continuous forms. The best removal efficiency was observed for high voltage gradient (2 V/cm) in a periodic form, which was 63.86. This result showed that a combination of periodic voltage application in addition to the employment of SDS is an effective method for hydrocarbon removal from low permeable sand.

• 한국지하수토양환경학회지:지하수토양환경
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• 제13권6호
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• pp.17-22
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• 2008

산순환 동전기적 정화기술의 아연과 니켈로 오염된 토양의 정화 타당성을 조사하였다. 1M HCl을 활용한 토양세척에서 아연과 니켈의 제거율은 각각 24%와 9%였으며, 산세척은 이 토양을 정화하기에 적합하지 않았다. 일반적인 동전기 정화 방법으로 28일 동안 운전한 결과, 아연과 니켈의 제거율은 산세척보다도 낮았다. 강산으로 음극을 순환시켜주어 토양 전체의 pH를 산성으로 조절한 실험에서 아연과 니켈의 제거는 비약적으로 증가하였다. 또한 강산으로 전처리한 토양에서는 그 제거율이 보다 많이 증가하였다. 이러한 실험결과를 근거로 볼 때 산순환 동전기 정화는 아연과 니켈로 오염된 토양을 정화하는데 매우 효과적인 것으로 판단된다.

• 한국환경농학회지
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• 제31권1호
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• pp.24-29
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• 2012

BACKGROUND: In recent years, microbial fuel cells (MFCs) have emerged as a promising technology for recovering renewable energy from waste biomass, especially wastewater. In this study, the possibility of bioelectricity generation in two chambered mediator-less microbial fuel cells (MFCs) was successfully demonstrated using fermentable and non-fermentable substrates. METHODS AND RESULTS: Two different electron acceptors have been tested in the cathode chamber for the effects of reducing agent on the power generation in MFCs. The average voltages of $0.26{\pm}0.014$ V and $0.36{\pm}0.02$ V were achieved with acetate using oxygen and potassium ferricyanide as reducing agent, respectively. Similarly, with glucose the average voltages of $0.256{\pm}0.05$ V and $0.340{\pm}0.04$ V were obtained using oxygen and ferricyanide, respectively. Using potassium ferricyanide as the reducing agent, the power output increases by 39 and 43% with acetate and glucose, respectively, as compared to the dissolved oxygen. Slightly higher coulombic efficiency (CE%) was obtained in acetate as compared to MFCs operated with glucose. The maximum power densities of 124 mW/$m^2$ and 204 mW/$m^2$ were obtained using dissolved oxygen and $K_3Fe(CN)_6$, respectively. CONCLUSION(s): This study demonstrates that power generation from the MFCs can be influenced significantly by the different types of catholyte. Relatively higher CE was obtained with $K_3Fe(CN)_6$. Thus, application of $K_3Fe(CN)_6$ as the catholyte can be vital for scaling uppower generation from the MFCs forreal time applications.

• Journal of Electrochemical Science and Technology
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• 제12권4호
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• pp.406-414
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• 2021

Electrochemical devices are constructed for continuous syngas (CO + H₂) production with controlled selectivity between CO₂ and proton reduction reactions. The ratio of CO to H₂, or the faradaic efficiency toward CO generation, was mechanically manipulated by adjusting the space volume between the cathode and the polymer gas separator in the device. In particular, the area added between the cathode and the ion-conducting polymer using 0.5 M KHCO₃ catholyte regulated the solution acidity and proton reduction kinetics in the flow cell. The faradaic efficiency of CO production was controlled as a function of the distance between the polymer separator and cathode in addition to that manipulated by the electrode potential. Further, the electrochemical CO₂ reduction device using Au NPs presented a stable operation for more than 23 h at different H₂:CO production levels, demonstrating the functional stability of the flow cell utilizing the mechanical variable as an important operational factor.

• Journal of Electrochemical Science and Technology
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• 제14권2호
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• pp.152-161
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• 2023

Vanadium redox flow batteries (VRFBs) have been considered one of promising power sources for large scale energy storage systems (ESS) because of their excellent cycle performance and good safety. However, VRFBs still have a few challenging issues, such as poor Coulombic efficiency due to vanadium crossover between catholyte and anolyte, although recent efforts have shown promise in electrochemical performance. Herein, the vanadium complexes with various glyme ligands have been examined as active materials to suppress vanadium crossover between catholyte and anolyte, thus improving the Coulombic efficiency of VRFBs. The conventional Nafion membrane has a channel size of ca. 10 Å, whereas vanadium cation species are small compared to the Nafion membrane channel. For this reason, vanadium cations can permeate through the Nafion membrane, resulting in significant vanadium crossover during cycling, although the Nafion membrane is a kind of ion-selective membrane. In this regard, various glyme additives, such as 1,2-dimethoxyethane (monoglyme), diethylene glycol dimethyl ether (diglyme), and tetraethylene glycol dimethyl ether (tetraglyme) have been examined as complexing agents for vanadium cations to increase the size of vanadium-ligand complexes in electrolytes. Since the size of vanadium-glyme complexes is proportional to the chain length of glymes, the vanadium permeability of the Nafion membrane decreases with increasing the chain length of glymes. As a result, the vanadium complexes with tetraglyme shows the excellent electrochemical performance of VRFBs, such as stable capacity retention (90.4% after 100 cycles) and high Coulombic efficiency (98.2% over 100 cycles).