• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.176-179
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• 2009

The performance of direct methanol fuel cells is affected by operating conditions such as, methanol feeding temperatures, methanol concentrations, and methanol flow rates during the operation in different environmental conditions. In this study, effects of the environmental temperature on performance of direct methanol fuel cells have been investigated in order to test a applicability of direct methanol fuel cell to the vehicle. The environmental temperature (ET) was varied from $-20^{\circ}C$ to $+30^{\circ}C$. The inside fuel cell temperature (CT) during test at various operating conditions was monitored and the performance of fuel cell was measured in the I-V polarization curve. With increasing the ET, the performance of the fuel cell was significantly improved and the CT also almost linearly increased. However, at below $0^{\circ}C$ ET, the DMFC showed very poor performance and needed to control CT or methanol feeding temperature (MFT), methanol flow rate(MFR) to obtain enough power of the vehicle.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.124.1-124.1
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• 2010

The impurities in the methanol fuel that is used for direct methanol fuel cell (DMFC) could greatly affect the performance of membrane electrode assemblies (MEA). The most common impurities in the commercial methanol fuel are mainly ethanol, acetone, acetaldehyde, or ammonia. In this study, the effect of impurities in methanol fuel was investigated on the performance of MEA. The MEA for DMFC were prepared using a semi-automatic bar-coating machine, which can prepare the catalyst layer with uniform thickness for MEA. As a result, a single cell supplied with one of the 6 different kinds of methanol fuels showed a significant degradation of the fuel cell performance. The most common impurities in the commercial methanol fuel is mainly ethanol, acetone, acetaldehyde, or ammonia. The effects of the kind and the concentration of impurities in the methanol fuels were investigated on the performance of MEA for DMFC. We will propose the optimum compositions and limit concentration of impurities in methanol fuel for high performance of MEA for DMFC.

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.1-5
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• 2008

A Pt-layer was deposited on the anode side of a Nafion membrane via a sputtering method in order to reduce methanol crossover in a direct methanol fuel cell (DMFC). The methanol permeation and the proton conductivity through the modified membranes were investigated. The performances of the direct methanol fuel cell were also tested using single cells with a Nafion membrane and the modified membranes. The Pt-layers on the membrane blocked both methanol crossover and proton transport through the membranes. Methanol permeability and proton conductivity decreased with an increase of the platinum layer thickness. At methanol concentration of 2 M, the DMFC employing the modified membrane with a platinum layer of 66 nm-thickness showed similar performance to that of a DMFC with a bare Nafion membrane in spite of the lower proton conductivity of the former. The maximum power density of the cell using the modified membrane with a platinum layer of 66 nm-thickness increased slightly while that of the cell with the bare membrane decreased abruptly when a methanol solution of 6M was supplied.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.3
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• pp.197-204
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• 2008

DMFC(Direct Methanol Fuel Cell) is one of promising candidates for power sources of small mobile IT devices like notebook, cell phone, and so on. Efficient operation of fuel cell system is very important for long-sustained power supply because of limited fuel tank size. It is necessary to investigate operation characteristics of fuel cell stack for optimal control of DMFC system. The generated voltage was modeled according to various operating condition; methanol concentration, stack temperature, and load current. It is inevitable for methanol solution at anode to cross over to cathode through MEA(membrane electrode assembly), which reduces the system efficiency and increases fuel consumption. In this study, optimal operation conditions are proposed by analyzing stack performance model, cross-over phenomenon, and system efficiency.

• Korean Journal of Materials Research
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• v.28 no.6
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• pp.330-336
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• 2018

In this study, a membrane electrode assembly(MEA) composed of three electrodes(anode, cathode, and reference electrode) is designed to investigate the effects of methanol concentration on the overpotentials of anode and cathode in direct methanol fuel cells(DMFCs). Using the three-electrode cell, in-situ analyses of the overpotentials are carried out during direct methanol fuel cell operation. It is demonstrated that the three-electrode cell can work effectively in transient state operating condition as well as in steady-state condition, and the anode and cathode exhibit different overpotential curves depending on the concentration of methanol used as fuel. Therefore, from the real-time separation of the anode and cathode overpotentials, it is possible to more clearly prove the methanol crossover effect, and it is expected that in-situ analysis using the three-electrode cell will provide an opportunity to obtain more diverse results in the area of fuel cell research.

• Macromolecular Research
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• v.16 no.6
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• pp.524-531
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• 2008

The mitigation or elimination of methanol crossover for perfluorosulfonic acid fuel cell membranes has been investigated extensively for direct methanol fuel cell applications with the aim of increasing the electrochemical performance and enhancing the utilization rate of methanol. Self-assembly modifications by applying an oppositely charged polyelectrolyte to Nafion membranes were attempted in order to block or reduce methanol crossover while maintaining the other advantageous properties of Nafion membranes. It was reported that anionic polyallylamine hydrochloride (PAH) was the most efficient polyelectrolyte in reducing methanol crossover, and considerable cell performance was obtained even at a methanol feed concentration of 10 M.

• Membrane Journal
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• v.14 no.1
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• pp.53-56
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• 2004

Direct Methanol Fuel Cell (DMFC) is considered as a candidate technology for applications in stationary, transportation as well as electronic power generation purposes. To develop a high performance direct methanol fuel cell(DMFC), a competent electrolyte membrane is needed. The electrolyte membrane should be durable and methanol crossover must be low. One of the approaches to increase the stability of generally used polymer electrolyte membranes such as Nafion against swelling or thermal degradation is to bond it with an inorganic material physically or chemically. In Noritake Company, we have developed a novel method of reinforcing the polymer electrolyte matrix with inorganic fibers. Methanol crossover values measured were significantly lower than the original polymer electrolyte membranes. These fiber reinforced electrolyte membranes (FREM) were used for DMFC study and stable power output values as high 160 mW/$\textrm{cm}^2$ were measured. The details of the characteristics of the membranes as well as I-V data of fuel cell stacks are detailed in the paper.

• Macromolecular Research
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• v.15 no.4
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• pp.379-384
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• 2007

Sulfonation of polyetheretherketones (PEEK) was carried out in order to fabricate commercial perfluorosulfonic acid membrane alternatives, which were characterized in terms of their ion exchange capacity, ionic conductivity, water swelling, methanol crossover and electrochemical performance in their direct application as a methanol fuel cell. A high ion exchange capacity, 1.88, was achieved with a sulfonation reaction time of 8 h, with a significantly low methanol crossover low compared to that of Nafion. However, the morphological stability was found to deteriorate for membranes with sulfonation reaction times exceeding 8 h. Electrochemical cell tests suggested that the fabrication parameters of the membrane electrode assembly based on the sulfonated PEEK membranes should be optimized with respect to the physicochemical properties of the newly prepared membranes.

• Journal of the Korean Electrochemical Society
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• v.4 no.2
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• pp.65-69
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• 2001

The potential change, and the crossover of alcohol in a liquid-feed solid polymer electrolyte fuel cell operating at atmosphere and room temperature was investigated. Alcohol crossover was generated from all the alcohol by using the fuel. The single-cell property of direct methanol fuel cell was higher than that of other alcohol species as $31mW/cm^2$ at 0.23 V at 4.5M of methanol.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.6
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• pp.467-473
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• 2008

This study is to investigate the influence of catalyst loading quantity on the direct methanol fuel cell (DMFC) performance. In this paper, Pt-Ru and Pt-black loading as the catalyst were varied from 1 to $4mg/cm^2$ at the anode and cathode, respectively. The experiment was conducted with single fuel cell consisted of $5cm^2$ effective electrode area, serpentine type flow pattern and Nafion 117 membrane. Also, AC impedance and methanol crossover current were measured to investigate the performance loss precisely. As a result, the performance of fuel cell was significantly increased with the increase of cathode catalyst loading. However, the performance did not increase further above a certain Pt-Ru catalyst loading as the increase of anode catalyst loading.