• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.101-104
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• 2007

Mechanical behavior in metal bipolar plate of a fuel cell stack was studied using finite element analysis. The fuel stack is essentially composed of a metal bipolar plate (metal BP), a gasket, an end plate, a membrane electrolyte assembly (MEA), and a gas diffusion layer (GDL). It is important to maintain a suitable fastening force of Metal BP, because it influences the power efficiency of the fuel cell stack. After a gasket and a GDL are placed on the metal BP, the reaction force with the displacement is measured. The channel of metal bipolar plate is replaced by a simple geometrical plate. The results of FEM are similar to those of experiment. Therefore mechanical behavior in metal BP of a fuel cell stack can be estimated by using FEM.

• Economic and Environmental Geology
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• v.51 no.2
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• pp.177-183
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• 2018

This study assessed an application of electrocoagulation (EC) for the removal of cobalt (Co) in radioactive liquid waste from nuclear power plant. The EC process is an electrochemical means to remove a contaminant in wastewater and a novel process to complement the disadvantage of chemical treatment and membrane process. Radioactive liquid waste has been produced from washing process of radio nuclide power plant cooling system. The EC process eliminates Co from the electrolyte within 10 min; in addition, the dewatered sludge produced in EC process is only 0.2 g. Therefore, the EC process is a promising technique for the removal of Co in radioactive liquid waste and volume reduction of wastes.

• Analytical Science and Technology
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• v.12 no.6
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• pp.472-477
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• 1999

It was developed the oxygen sensor of air-fuel ratio measuring system that was controlled the needed air amounts in optimum combustion according to the analysis of oxygen concentration of exhaust gas. The oxygen sensor was prepared by using gold as cathode, which the detection range for the oxygen concentration was from 0.0% to 30.0%. Response time was observed 15 to 20 sec. rapidly and selectively. It was appeared a good result in reproducibility and stability.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.8
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• pp.48-56
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• 2009

This paper presents the power conversion system for TIG-welder using the fuel cell stack Generally, power supply for TIG-welder uses the front-ended diode bridge rectifier by common AC power source. In this case, power supply of TIG-welder increases in volume because of using bulky capacitor and diode-rectifier. Also, input current includes ripple and harmonics. Moreover, TIG-welder will be demand the power supply with lightweight and easy movement in the areas like as the islands and mountainous areas or the special environment are not use common AC power source. Thus, input power of the power conversion system for TIG-welder is used PEMFC(Polymer Electrolyte Membrane Fuel Cell), and the power conversion system is comprised of full-bridge converter with function of boost converter and inverter welding source, in this paper. The proposed power conversion system which is power supply for TIG-welder was verified by computer simulations and experiments.

• Proceedings of the Korean Magnestics Society Conference
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• 2011.06a
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• pp.129-129
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• 2011

The limited understanding of the surface properties of $Pt_3Ni$ for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cell (PEMFC) has motivated the study of properties and electronic structures of seven layered $Pt_3Ni$ (001), (110), and (111) surfaces. The first principle method based on density functional theory (DFT) is carried out. It is found that the bulk $Pt_3Ni$ has a ferromagnetic ground state with the ordered fcc type L12 structure, which is in good agreement with other results. Non magnetic Pt has the induced magnetic moment due to the strong hybridization between 3d Ni and 5d Pt. The magnetic moment of Pt and Ni enhanced on the surface of each due to surface effect however the magnetic moment of surface Pt in the Pt-segregated Pt3Ni (111) decreased and the magnetic moment of Ni in Ni rich subsurface increased significantly. The calculated d band centers of Pt explain the possibilities for oxygen absorption and play the important roles in altering the catalytic properties. The spin polarized densities of states are presented in order to understand physical properties of Pt in different surfaces in detail.

• Journal of Hydrogen and New Energy
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• v.15 no.1
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• pp.23-31
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• 2004

For the fabrication of high efficient bifunctional electrocatalyst of oxygen electrode for PEM URFC (Polymer Electrolyte Membrane Unitized Regenerative Fuel Cell), which is a promising energy storage and conversion system using hydrogen as the energy medium, several bifunctional electrocatalysts were prepared and tested in a single cell URFC system. The catalysts for oxygen electrode revealed fuel cell performance in the order of Pt black > PtIr > PtRuOx > PtRu ~ PtRuIr > PtIrOx, whereas water electrolysis performance in the order of PtIr ~ PtIrOx > PtRu > PtRuIr > PtRuOx ~ Pt black. Considering both reaction modes PtIr was the most effective elctrocatalyst for oxygen electrode of present PEM URFC system. In addition, the water electrolysis performance was significantly improved when Ir or IrOx was added to Pt black just 1 wt.% without the decrease of fuel cell performance. Based on the catalyst screening and the optimization of catalyst composition and loading, the optimum catalyst electrodes for PEM URFC were $1.0mg/cm^2$ of Pt black as hydrogen electrode and $2.0mg/cm^2$ of PtIr (99:1) as oxygen electrode.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.6
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• pp.553-561
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• 2012

Existing energy sources convert chemical energy into mechanical energy, while fuel cell directly generates electricity through an electrochemical reaction between hydrogen and oxygen. Therefore, it has a lot of strong points such as high efficiency, zero emission, and etc. In addition, with the development of hydrogen preservation technique, some companies have been researching and releasing portable fuel cell power packs for specific applications like military equipment, automobile, and so on. However, there are some drawbacks to the fuel cell, high cost and slow dynamic response. In order to compensate these weak points, auxiliary energy storages could be applied to the fuel cell system. In this paper, the optimum structure for a 150W portable fuel cell power pack with a battery pack is selected considering the specification of the system, and the design process of main parts is described in detail. Here, main objectives are compact size, simple control, high efficiency, and low cost. Then, an automatic mode change algorithm, which converts the operating mode depending on the states of fuel cell stack, battery pack, and load, is introduced. Finally, performance of the designed prototype using the automatic mode change control is verified through experiments.

• Journal of Hydrogen and New Energy
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• v.19 no.6
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• pp.498-504
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• 2008

Metal-reducing bacterium, Geobacter sulfurreducens is available for mediator-less microbial fuel cell (MFC) because it has biological nanowires(pili) which transfer electrons to outside the cell. In this study, in the anode chamber of the MFC system using G. sulfurreducens, the concentrations of NaCl, sodium phosphate and sodium bicarbonate as electrolytes were mainly optimized for the generation of electricity from acetate. 0.4%(w/v) NaClO and 0.5M $H_2SO_4$ could be utilized for the sterilization of acrylic plates and proton exchange membrane (major construction materials of the MFC reactor), respectively. When NaCl concentration in anode phosphate buffer increased from 5 to 50 mM, power density increased from 6 to $20\;mW/m^2$. However, with increasing sodium phosphate buffer concentration from 5 to 50 mM, power density significantly decreased from 18 to $1\;mW/m^2$. Twenty-four mM sodium bicarbonate did not affect electricity generation as well as pH under 50 mM phosphate buffer condition. Optimized anode chamber of MFC using G. sulfurreducens generated relatively high power density ($20\;mW/m^2$) with the maximum coulombic efficiency (41.3%).

• Journal of Hydrogen and New Energy
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• v.23 no.6
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• pp.640-646
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• 2012

The effect of Ce promotion over 1wt% $Pt/{\gamma}-Al_2O_3$ catalysts on the CO conversion and $CO_2$ selectivity was investigated in preferential CO oxidation (PrOx) to reduce the CO concentration less than 10 ppm in excess $H_2$ stream for polymer electrolyte membrane fuel cell (PEMFC). Ce-promoted 1wt% $Pt/{\gamma}-Al_2O_3$ catalysts were prepared by incipient wetness impregnation method and the loading amount of Pt was fixed at 1wt%. The content of Ce promoter which has excellent oxygen storage and transfer capability due to the redox property was adjusted from 0 to 1.5wt%. Ce-promoted 1wt% $Pt/{\gamma}-Al_2O_3$ catalysts exhibit high CO conversion and $CO_2$ selectivity at low temperatures below $150^{\circ}C$ due to the improvement of reducibility of surface PtOx species compared with the 1wt% $Pt/{\gamma}-Al_2O_3$ catalyst without Ce addition. When Ce content was more than 1wt%, the catalytic activity was decreased at over $160^{\circ}C$ in PrOx because of competitive $H_2$ oxidation. As a result, 0.5wt% Ce is optimal content not only to achieve high catalytic activity and good stability at low temperatures below $150^{\circ}C$ in the presence of $CO_2$ and $H_2O$ but also to minimize the $H_2$ oxidation at high temperatures.

• Journal of Hydrogen and New Energy
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• v.22 no.4
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• pp.488-494
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• 2011

Gasket plays an important role on sealing of the polymer electrolyte membrane fuel cell (PEMFC) stack. Stack requires gaskets in each cell to keep the hydrogen and air/oxygen within their respective regions. The failure of the gasket creates the problems of fuel leakage, mixing, damage on parts and can be a direct reason for the degrading the efficiency of fuel cell. The purpose of this paper researches on how mechanical properties of EPDM gasket in PEMFC are changed after long-term operations. The EPDM (ethylenepropylene-diene monomer) gaskets are obtained from the stack after long-term operations. DMA (dynamic mechanical analysis) is conducted to access the change of mechanical properties of the EPDM gasket. SEM/EDS (scanning electron microscope/energy dispersive spectroscopy) was used to show the surface topography and chemical characterization on the sample surface.