• Journal of the Korean Electrochemical Society
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• v.19 no.2
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• pp.39-44
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• 2016

Oxygen reduction reaction in the fuel cell (ORR) plays a dominant role in the overall reaction. In addition, the low compatibility between the membrane and the binder consisted of different materials, greatly reduces the efficiency of the fuel cell performance. In view of these two problems, geometrically modified copolymers with 9.9_Bis (4-hydroxyphenyl) were synthesized via condensation reaction instead of conventional biphenol and were adopted as hydrocarbon ionomer binders. By utilizing these binders, two kinds of MEAs using fluorinated Nafion membrane and hydrocarbon based membrane were manufactured in order to electrochemical performance evaluation. With current-voltage curves, there was no significant difference in the 0.6 V when two types of membrane were applied. Also, tafel slope became considerably lower as compared to the Nafion membrane. Thus, it is determined that the new hydrocarbon binder is expected to contribute the improvement in performance of fuel cells.

• Clean Technology
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• v.27 no.4
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• pp.277-290
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• 2021

A supercapacitor, also called an ultracapacitor or an electrochemical capacitor, stores electrochemical energy by the adsorption/desorption of electrolytic ions or a fast and reversible redox reaction at the electrode surface, which is distinct from the chemical reaction of a battery. A supercapacitor features high specific power, high capacitance, almost infinite cyclability (~ 100,000 cycle), short charging time, good stability, low maintenance cost, and fast frequency response. Supercapacitors have been used in electronic devices to meet the requirements of rapid charging/discharging, such as for memory back-up, and uninterruptible power supply (UPS). Also, their use is being extended to transportation and large industry applications that require high power/energy density, such as for electric vehicles and power quality systems of smart grids. In power generation using intermittent power sources such as solar and wind, a supercapacitor is configured in the energy storage system together with a battery to compensate for the relatively slow charging/discharging time of the battery, to contribute to extending the lifecycle of the battery, and to improve the system power quality. This article provides a concise overview of the principles, mechanisms, and classification of energy storage of supercapacitors in accordance with the electrode materials. Also, it provides a review of the status of recent research and patent, product, and market trends in supercapacitor technology. There are many challenges to be solved to meet industrial demands such as for high voltage module technologies, high efficiency charging, safety, performance improvement, and competitive prices.

• Journal of the Korean Society for Environmental Technology
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• v.19 no.6
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• pp.536-542
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• 2018

A system combining an electrochemical method and an adsorption system using activated carbon was assessed to facilitate the reuse of cabbage-salting brine. IrOx/Ti insoluble catalyst electrodes were used in the experiment. The results were analyzed to identify any changes in the residual chlorine concentration according to variations in the current density at a salinity of 10 %, as well as the capacity of the activated carbon to adsorb the residual chlorine and organic matter. For current densities of $500A/m^2$ and $1,000A/m^2$, the residual chlorine concentration did not increase, instead stabilizing once the current reached 0.33 Ah/L. To assess the adsorption efficiency according to the residual chlorine concentration, the unit amount of the adsorption can be estimated from $Y=0.0066+2.087{\times}10^{-4}b$. For both residual chlorine generation using an electrochemical method and chlorine removal through activated-carbon adsorption, the unit amount of adsorption was 0.33 g/g. The maximum amount of $COD_{Cr}$ organic matter adsorbed by the activated carbon was 0.021 g/g, while for $COD_{Mn}$, the value was 0.004 g/g.

• New Physics: Sae Mulli
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• v.68 no.12
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• pp.1315-1323
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• 2018

We studied the carbonization due to the annealing condition of waste coffee powder for application as an active anode material for lithium-ion batteries (LIBs). The coffee powder used as an active anode material for LIBs was obtained from coffee beans, not from a coffee shells. The waste coffee powder was dried in air and heat-treated in an $Ar/H_2$ atmosphere to obtain a pore-forming activated carbon powder. The specific capacity of the sample annealed at $700^{\circ}C$ was still 303 mAh/g after 1000 cycles at a current density of 1000 mA/g and with a coulombic efficiency of over 99.5%. The number of pores and the pore size of the waste coffee powder were increased due to chemical treatment with KOH, which had the some effect as an increased specific surface area. The waste coffee powder is considered to be a very promising active anode material because of both its excellent electrochemical properties due to enhanced carrier conduction and its being a cost effective resource for use in LIBs.

• Resources Recycling
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• v.31 no.3
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• pp.61-72
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• 2022

We investigated the electrochemical behavior of Sn (93.0 %)-Ag (4.06 %)-Cu (0.89 %) during electrolysis of Pb-free solder waste to recover tin and silver. A thin strip of the solder waste produced by high-temperature melting and casting was used as a working electrode to perform electrochemical analysis. During anodic polarization, the current peak of an active region decreased with an increase in the concentration of sulfuric acid used as an electrolyte. This resulted in the electro-dissolution of the working electrode in the electrolyte (1.0 molL^-1 sulfuric acid) for a constant current study. The study revealed that the thickening of an anode slime layer at the working surface continuously increased the electrode potential of the working electrode. At 10 mAcm^-2, the dissolution reaction continued for 25 h. By contrast, at 50 mAcm^-2, a sharp increase in the electrode potential stopped the dissolution in 2.5 h. During dissolution, silver enrichment in the anode slime reached 94.3% in the 1 molL^-1 sulfuric acid electrolyte containing a 0.3 molL^-1 chlorine ion, which was 12.7% higher than that without chlorine addition. Moreover, the chlorine enhanced the stability of the dissolved tin ions in the electrolyte as well as the current efficiency of tin electro-deposition at the counter electrode.

• Journal of the Korean Electrochemical Society
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• v.17 no.2
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• pp.94-102
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• 2014

Cation exchange membrane (Nafion) was modified to reduce the vanadium ion permeation through the membrane and to increase the vanadium redox flow battery (VRB) system performance by coating the graphene oxide (GO) which has nano-plate like morphology. Modified membrane properties were studied by measuring the ion exchange capacity (I.E.C), water uptake and proton conductivity. The thickness of the coated layer on the surface of the Nafion membrane was observed as $0.93{\mu}m$ by SEM. Proton conductivity and vanadium ion permeability of the modified membrane were decreased to 27% and 25% compared to that of the commercial Nafion membrane respectively. VRB single cell performance test was performed to compare the system performance of the VRB applied with commercial Nafion membrane and modified membrane. VRB system applied with modified membrane showed higher coulombic efficiency and energy efficiency than the VRB system applied with the commercial Nafion membrane due to the reduction of the vanadium ion permeation. From these result, we could suggest that the membrane modification by coating the GO on the surface of the Nafion membrane could be one of the promising strategies to reduce the vanadium ion permeation and to increase the VRB system performance effectively.

• Journal of the Korean Electrochemical Society
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• v.17 no.1
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• pp.37-43
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• 2014

In this study, capacitive deionization (CDI) was introduced for desalination of mining water. Ion-exchange polymer coated carbon electrodes (IEE) were used in CDI to desalt mining water. The CDI performance using the IEE for desalination of mining water was carried out and then was compared with that using general carbon electrodes without ion-exchange polymer coating (GE). Moreover, to investigate the effect of the concentration of influent solutions on CDI performance, the CDI performance using the IEE for desalination of brackish water (NaCl 200 ppm) was also performed and analyzed. As a result, the higher salt removal efficiency, rate and the lower energy consumption in the CDI process using the IEE and mining water were obtained compared with those using the GE and mining water. It is mainly due to higher non-Faradaic current, low ohmic resistance of the influent, overlapping effect of electric double layers in micropore of the electrode. In addition, the CDI process using the IEE and brackish water shows much higher salt removal efficiency and lower salt removal rate than that using the IEE and mining water. This results from the lower concentration (i.e., higher ohmic resistance) and salt amount of the influent.

• Journal of the Korean Electrochemical Society
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• v.7 no.3
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• pp.143-147
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• 2004

An investigation upon the characterization of MCMB anodes with different vapor grown carbon fiber (VGCF) content for application in lithium polymer battery(LPB) was carried out. When VGCF material was used as conducting agent with MCMB active material, the impedance and the initial coulombic efficiency of test cells were found to decrease with the increasing amount of VGCF. On the other hand, as a function of added VGCF the discharge capacity and the utilization linearly with increased. Impedance of test cell with MCMB anode containing $6wt\%$ VGCF exhibited the lowest value whereas the impedance of $8wt\%$ VUF contained anode was similar to that of MCMB anode without VGCF. Interestingly, $6wt\%$ VUF contained anode showed the best battery characteristics. Internal resistance and rate capacity of the cell were. respectively, $0.918{\Omega}\;at\;25C\;and\;93\%$ at 2C. Generally, rate capability and the cycleability of MCMB based test cells with $4\~6wt\%$ VGCF content exhibited better results than the other cells. In the case of $6wt\%$ VGCF containing anode, the discharge capacity of the cell faded slowly with an ultimate charge-discharge cycling capacity of 178mAh/g at the 100th cycle. Thereafter, the discharge capacity faded negligibly and the utilization of the cell at the 100th cycle was more than $90\%$. The effect of addition of VGCF is discussed in detail.

• Microbiology and Biotechnology Letters
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• v.35 no.1
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• pp.73-80
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• 2007

Biofilm media was equipped in two-compartmented wastewater treatment bioreactor which was separated by porcelain septum. DC 2.0 volt of electric potential was charged to anodic (oxidative) biofilm media (ABM) to induce oxidation potential but not to that of carbon (neutral) biofilm media (CBM) that was used for control test. Biofilm structure, biomass variation, Off variation and wastewater treatment efficiency in the bioreactor equipped with ABM (ABM-bioreactor) and CBM (CBM-bioreactor). Time-coursed variation of biofilm structure forming on surface of ABM and CBM was observed by scanning electron microscopy. The biofilm growing on ABM was dispersed on surface and was not completely covered the media but the biofilm growing on CBM was continuously increased and finally covered the media. The ORP of CBM was decreased to 100 mV, which was reciprocally proportional to the biomass growth. However, the ORP of ABM was about 800 mV, which was maintained during operation for about 60 days. The treatment efficiency of COD in the ABM bioreactor was 2 times higher than those in the CBM bioreactor. From these results, we proposed that electrochemical oxidation potential charged to biofilm media may inhibit formation of biofilm extremely condensed and activate bacterial cell metabolism.

• Journal of the Korean Electrochemical Society
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• v.15 no.1
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• pp.41-47
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• 2012

An annular flow type of copper electrolysis reactor was setup in order to generate the copper ions to remove algae in water. The operating characteristics of the reactor and the effect of copper ion on algae have been considered. By controling the applied current, the copper ion concentration could be obtained as desired level and the faradaic efficiency was above 90%. When the flow rate was increased, the copper ion concentration was linearly decreased due to the dilution effect and the effect of concentration overpotential was insignificant. With the increase of pH in water, the copper ion concentration was linearly decreased and not affected by the conductivity of the water. The concentration of chlorophyll-a was sharply decreased with the increase of copper ion concentration. The algae was effectively removed as the copper ion concentration was above 0.2 ppm. There was no difference between the copper ions obtained by dissolving copper sulfate and those produced by copper electrolysis. The algae removal efficiency was above 90% after 5 days as the copper ion concentration was above 0.4 ppm.