• Clean Technology
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• v.10 no.2
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• pp.53-59
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• 2004

Direct methanol fuel cells (DMFC) are presently paid attention due to their higher energy density and portability. In order to slove problems such as high anodic overpotential and methanol crossover in DMFC, an analytical analysis for electrochemical model using Tafel equation and limiting current density was performed. Change of operational parameters such as temperature, transfer coefficients and membrane thickness results in helpful informations on voltage-current curves.

• Macromolecular Research
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• v.13 no.6
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• pp.514-520
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• 2005

Composite membranes of Nafion and sulfonated poly(arylene ether sulfone) were prepared. Sulfonated poly(arylene ether sulfone)s with different degrees of sulfonation were blended with Nafion to reduce the methanol crossover. The morphology, proton conductivity and methanol permeability of the resulting composite membranes were investigated by SEM, EDAX, AC impedance spectroscopy and permeability measuring instrument. The cross­sections of the composite membranes showed a phase separated morphology. The morphology and phase separation mechanism could be controlled by varying the blend ratio and the degree of sulfonation of poly(arylene ether sulfone). These complex morphologies can be applied for reducing methanol crossover. The methanol permeability and proton conductivity of the composite membranes were lower than those of Nafion 117 membrane since the development of an ionic pathway in the blend membrane was more difficult than that in Nafion itself.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.127-128
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• 2006

Nafion/basic polymer composite membranes were prepared to reduce the methanol crossover for the application of direct methanol fuel cell. The thermal and mechanical properties increased with increasing basic polymer contents due to the formation of complex via acid/basic interaction. The water uptake, proton conductivity, methanol permeability decreased with increasing basic polymer concentration by reduction of acidity associated with the formation of acid/base complex. The molecular effect on those properties was not considerable.

• 한국전기화학회:학술대회논문집
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• 2003.07a
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• pp.199-201
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• 2003

• Journal of the Korean Electrochemical Society
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• v.5 no.2
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• pp.68-73
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• 2002

Modified polymer electrolyte membranes were fabricated by the applying dc magnetron sputter-deposited Pd thin layers on the surface of the $Nafion^{TM}$ membranes in argon atmosphere. The Pd thin films were characterized by investigating its morphology, methanol permeability, and protonic conductivity. The performance of a direct methanol fuel cell(DMFC) with the modifed polymer electrolyte membrane was also tested by the measurement of its currents and voltages under flowing methanol. The Pd thin film could be a barrier layer to methanol crossover, but the protonic conductivity of the modified polymer membrane was reduced. By using the modified polymer eletrolyte membranes, both the methanol permeability and the protonic conductivity were decreased with increasing the thickness of Pd thin film. However, the performances of DMFC were almost independent on the thickness of Pd thim films. The efffcts of methanol concentration in a feeding fuels on the protonic conductivity and the cell performance were also investigated.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.204-207
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• 2007

DMFC(direct methanol fuel cell)는 액체연료의 이동과 저장의 용이성 때문에 이동용 장치를 위한 전원공급 장치로서 오랫동안 관심을 받아왔다. 하지만 methanol crossover는 DMFC의 상용화 이전에 해결해야 할 문제이다. 이를 위해 많은 분야에서 연구가 진행되고 있고, 그중에서 methanol에 저항성을 가진 촉매의 개발에 활발히 연구가 진행되고 있다. 본 연구에서는, 표연개질 된 PtCo/C 촉매를 사용하여 메탄올에 저항성을 가진 촉매를 합성하였다. 합성된 촉매의 size와 morphology를 알아보기 위해 transmission electron microscopy (TEM)를 사용하였다. 또한 methanol 존재 하에 산소환원반응의 activity를 알아보기 위해 Rotating ring disk electrode(RRDE) test를 하였고, MEA를 제작하여 full cell test도 병행하였다.

• Journal of the Korean Electrochemical Society
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• v.12 no.3
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• pp.245-250
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• 2009

Crosslinked membrane based on sulfonated polyimide was prepared by the introduction of crosslinkable monomer in polymerization process and crosslinking during membrane casting. Crosslinked membranes showed different properties from non-crosslinked membranes. Crosslinking decreased methanol crossover and therefore unit cell using crosslinked membrane showed increased open circuit voltage, 0.81 V, in comparison with unit cell using noncrosslinked membrane, 0.71 V. In addition, water uptake of crosslinked membrane, 40.5%, was lower than that of non-crosslinked membrane, 57.0%, and this resulted in improved dimensional stability. However, proton conductivity of crosslinked membranes showed rather low relative to non-crosslinked membrane due to reduced water uptake.

• Journal of Aerospace System Engineering
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• v.1 no.2
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• pp.21-26
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• 2007

DMFC(Direct Methanol Fuel Cell) has been considered as an attractive option to produce electric power in many application. In this study, in order to estimate the effects of the methanol concentration, wind velocity and temperature on the performance of DMFC, a physical prototype of DMFC was designed and manufactured, and the stack voltage of DMFC was measured during the operation of DMFC. Expecially, the experimental results showed that a low stack temperature, a low wind velocity and an excess methanol concentration lead to the increase of the time to reach the maximum stack voltage.

• 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.

• Clean Technology
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• v.10 no.1
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• pp.9-17
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• 2004

Direct methanol fuel cell(DMFC) with proton exchange membrane (PEM) has advantages over the conventional power source (e.g. vehicle). DMFC, however, has a problem to be solved such as methanol crossover, high anodic overpotential and limiting current density, etc. The physicochemical phenomena in DMFC can be described by coupled PDEs (partial differential equations), which can be solved by a PDE solver. In this paper, we utilized a commercial software FEMLAB to solve the PDEs. The FEMLAB is one of the software programs available which are developed as a solver for building physics problems based on PDEs and is designed to simulate systems of coupled PDEs which may be 1D, 2D, 3D, non-liner and time dependent. We performed simulation using the Tafel equation as an electrochemical reaction model to analyze methanol concentration profile in DMFC system. We confirm that the rapid decrease of methanol concentration at anodic catalyst layer with the increase of the current density is a main reason of the low performance in DMFC through simulation results.