• Korean Chemical Engineering Research
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• v.45 no.4
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• pp.345-350
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• 2007

During PEMFC operation, OCV(open circuit voltage) and low humidity conditions accelerate the degradation of perfluorosulfonic acid membrane. There have been no studies that clearly explain why these conditions accelerate the membrane degradation. In this study, the hydrogen permeability through the membrane, I-V polarization of MEA, fluoride emission rate(FER) and $H_2O_2$ concentration in condensed water were measured during cell operation under OCV and low relative humidity(RH). The experimental results were evaluated with oxygen radical mechanism the most commonly known for membrane degradation. It seems that low RH of anode is a good condition for $H{\cdot}$ radical formation on the Pt catalyst and the OCV condition accelerate the $H{\cdot}$ to form $HO_2{\cdot}$ radical attacking the polymer membrane.

• Journal of the Korean Electrochemical Society
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• v.18 no.4
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• pp.172-181
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• 2015

Solid Oxide Fuel Cells (SOFC) continue to be among the most promising alternative energy devices. This paper addresses i-V characteristics of SOFC with a focus on air flow rate along the planar anode electrodes. To address this, detailed Butler-Volmer kinetics are implemented in a general-purpose CFD code FLUENT. The numerical results were validated against experimental data from the literature showing excellent match with i-V polarization data ranging 1V-0.4V. Numerical calculations of fuel cell operation under different flow rare conditions were performed in three-dimensional geometries. Results are presented in terms of concentration distribution of hydrogen, oxygen, and water. The simulations and results indicate that advanced CFD with UDF(User-Defined Function) of Butler-Volmer kinetics can be used to identify the conditions leading to air flow rate and specific surface area and guide development of operating conditions and improve the fuel cell system performance.

• Journal of the Korean Electrochemical Society
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• v.6 no.2
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• pp.145-152
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• 2003

Capacitance of a hybrid capacitor that has characteristics of both electrolyte capacitor and supercapacitor is determined by anode surface covered with oxide layer. In this study, optimal condition processes for anode to fabricate a high voltage hybrid capacitor was investigated. We mixed aluminum powder having mean particle size of $40{\mu}m$ with NaCl powders at weight ratio of 4 : 1 and prepared a disk type electrode after annealing at various temperature. After dissolving NaCl in $50^{\circ}C$ distilled water, heat treatment, eletropolishing, chemical treatment, and the first and the second etching of Al disk were conducted. In each process, capacitances and resistances of the disk measured by ac-impedance analyzer were compared to find its optimum treatment condition. Also, the surface morphology of treated disks were observed and compared by SEM. After the second etching, the Al disk was anodized at 365V to make an anode of hybrid supercapacitor that can be operated at 300V, Capacitance and resistance of the anodized Al disk electrode was compared with those of commercialized conventional aluminum electrolytic capacitor at different frequencies.

• Journal of Adhesion and Interface
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• v.19 no.3
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• pp.101-105
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• 2018

With the rapidly growing of the population and industrization of cities, the clean and affordable water resources have gained immense interest because of remaining about 780 million people still lack access to it. However, present wastewater treatment systems have been faced with various issues, such as low processing efficiency, high operational costs and the requirement of a large area for manufacturing. It is therefore urgently required to develop an inexpensive and efficient wastewater treatment system. As the one of these efforts, we suggested and successfully demonstrated the wastewater treatment system using and electrochemical method via a dimensionally stable anode (DSA) based on rutile type $RuO_2$. Our system achieved biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total organic carbon (TOC) removal efficiently at the respective rates of 52.0%, 77.8%, and 65.6% from household wastewater. In addition, we were able to remove BOD, COD, total nitrogen (TN), and total phosphorus (TP) from animal husbandry wastewater at rates of 92.9%, 75.6%, 35.1%, and 100%, respectively, thereby achieving dramatic reductions. Considering the excellent removal efficiency and the small size of this device, electrochemical wastewater treatment using a DSA coated in rutile $RuO_2$ presents a promising option for the treatment of both household and animal husbandry wastewater.

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.51-58
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• 2008

Many researches for effects of different flow configurations on performance of Proton Exchange Membrane Fuel Cell have extensively been done but the effects of flow direction at the same flow channel shape should be considered for optimal operation of fuel cell as well. In this paper a numerical computational methode for simulating entire reactive flow fields including anode and cathode flow has been developed and the effects of different flow direction at parallel flow was studied. Pressure drop along the flow channel and density distribution of reactant and products and water transport, ion conductivity across the membrane and I-V performance are compared in terms of flow directions(co-flow or counter-flow) using above numerical simulation method. The results show that the performance under counter-flow condition is superior to that under co-flow condition due to higher reactant and water transport resulting to higher ion conductivity of membrane.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.9
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• pp.1201-1208
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• 2002

A numerical flow-field analysis is performed to investigate flow configurations in the anode, cathode and cooling channels on the bipolar plates of a proton exchange membrane fuel cell (PEMFC). Continuous open-faced flow channels are formed on the bipolar plate surface to supply hydrogen, air and water. In this analysis, two types of channel pattern are considered: serpentine and spiral. The averaged pressure distribution and velocity profiles of the hydrogen, air and water channels are calculated by two-dimensional flow-field analysis. The equations for the conservation of mass and momentum in the two-dimensional fluid flow analysis are slightly modified to include the characteristics of the PEMFC. The analysis results indicate that the serpentine flow-fields are locally unstable (because two channels are cross at right angles). The spiral flow-fields has more stable than the serpentine, due to rotational fluid-flow inertia forces. From this study, the spiral channel pattern is suggested for a channel pattern of the bipolar plate of the PEMFC to obtain better performance.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.5
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• pp.580-587
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• 2004

The objective of this research is to investigate the electrochemical oxidation process for nitrogen removal in wastewater involving chloride ion and nitrogen compounds. The process experiment of electrochemical oxidation was conducted by using the stainless steel tube type reactor and the $Ti/IrO_2$ as anode. Free chlorine production and current efficiency variation for total nitrogen removal was compared depending on whether electrolyte is added, and the nitrogen type distribution under an operating condition. When chloride was added as electrolyte, it was found that production of free chlorine increased and the concentration of the chloride decreased as retention time passed. The concentration of chloride in influent decreased from 1,660 to 1,198 mg/L at the current density of $6.7A/dm^2$, while concentration of free chlorine increased to 132 mg/L. Current efficiency in removal of ammonium nitrogen was increased when chloride was dosed as electrolyte. It was observed that ammonium nitrogen was oxidized to nitrite and nitrate through electrochemical oxidation and that the concentration of total nitrogen in influent was reduced from 22.58 to 4.00 mg/L at the short retention time of 168 seconds through the electrochemical oxidation of nitrogen.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.336-340
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• 2009

This paper presents experimental results carried out on the purge characteristic of the anodic dead-end mode fuelcell and how to improve the cell performance by pulsation effects. The dead-end mode fuelcell has some merits that a fuel supplying device is not needed and the cell power is higher than that in the open mode fuelcell. However, the purge is necessary for preventing the porous media from being flooded by liquid water formed in the channel. At this time, the un-reacted fuel is discharged with the liquid water together in purge process. The discharged fuel can make the fuel efficiency lower. Therefore, the number of purge times should be decreased for the better fuel efficiency. In this study, the outlet of the anode channel was equipped with a purge solenoid valve and a pulsation generator. The purge times was decreased when the current density decreased and operation pressure increased without the pulsation effects. In addition, when the pulsation effects such as various frequencies or amplitudes were applied, purge times was alleviated up to 40%.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.3
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• pp.355-360
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• 2012

The characteristics of power generation were investigated by changing the electrical conductivity from 10 to 40mS/cm using air-cathode microbial fuel cell, which had graphite fiber fabric(GFF) anode. There were three kinds of cathode used: one was carbon cloth cathode coated with Pt, another was carbon nanotube(CNT) cathode with non-precious catalyst of Fe-Cu-Mn, and the other was carbon nanotube(CNT) cathode without any catalyst. When it was operated in batch mode, power density of 1369.5mW/$m^2$ was achieved at conductivity of 20mS/cm. Power density from MFC with CNT cathode coated with multi-catalyst of Fe-Cu-Mn was shown about 985.55mW/$m^2$, which was 75.1% compared the power density of carbon cloth coated with Pt. This meant that CNT cathode coated with multi-catalyst of Fe-Cu-Mn could be an alternative of carbon cloth cathode.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.5
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• pp.503-509
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• 2016

Fuel cell is a device for producing electricity by using the hydrogen produced by the fuel processor. At this time, CO is also created by the fuel processor. The resulting CO enters the stack where is produce electricity and leads to the adsorption of anode catalyst, finally the CO poisoning occurs. Stack which occurred CO poisoning has a reduction in performance and shelf life are gradually fall because they do not respond to hydrogen. In this paper, experiments that using a PROX reactor to prevent CO poisoning were carried out for removing the CO concentration to less than 10ppm range available in the fuel cell. Furthermore experiments by the PROX reaction was designed and manufactured with a water-cooling heat exchange reactor to maintain a suitable temperature control due to the strong exothermic reaction.