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

• Korean Membrane Journal
• /
• v.10 no.1
• /
• pp.46-52
• /
• 2008

Optimization of ionomer solution was conducted in order to improve the performance of MEAs in PEMPC. The interface between membrane and electrodes in MEAs is crucial region determining fuel cell performance as well as ORR reaction at cathode. Through the modification of Nafion ionomer content at the interface between membrane and electrodes, an optimal content was obtained with Nafion 115 membranes. Two times higher current density was obtained with the outer Nafion sprayed MEA compared with the non-sprayed one. In addition, the symmetrical impedance spectroscopy mode (SM) exhibited that the resistances of membrane area, proton hydration, and charge transfer decreased as the outer Nafion is sprayed. From the polarization curves and SM, the highest current density and the lowest resistance was obtained at the outer ionomer content of $0.15\;mg\;cm^{-2}$.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.06a
• /
• pp.169-171
• /
• 2007

A breaking layer was introduced to conventional decal transfer method in membrane electrolyte assembly fabrication for high catalyst transfer ratio. In this study, the modified decal transfer method with high catalyst transfer ratio was introduced and its performance is studied. The structural features of electrodes made by decal method were investigated using scanning electron microscopy and current-voltage polarization measurement.

• Journal of Microbiology and Biotechnology
• /
• v.15 no.2
• /
• pp.438-441
• /
• 2005

A mediator-less microbial fuel cell (MFC) was used to determine the performance effects of a membrane­electrode assembly (MEA). The MFC with an MEA generated a higher current with an increased coulomb yield when compared to an MFC with a separate cathode. Less oxygen was diffused through an MEA than through a Nafion membrane. The MFC performance was improved with a buffer, although a high-strength buffer reduced the performance.

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.06a
• /
• pp.110-112
• /
• 2006

Membrane electrode assembly (MEA) for polymer electrolyte fuel cell (PEFC) are commonly prepared in the research laboratory by spraying, screen-printing and brushing catalyst slurry onto membrane or other support material like carbon paper or polyimide film in a batch style. These hand applications of the catalyst slurry are painstaking process with respect to precision of catalyst loading and reproducibility. It has been generally mentioned that the adoption of continuous process is very helpful to develop the reliable product. In the present work, we report the results of using continuous type coater with doctor-blade to coat catalyst slurry for preparing the MEA catalyst layers In a faster and highly reproducible fashion. We show that while expectedly faster than batch style, the machine coater requires the use of slurry of appropriate composition and a properly selected transfer decal material in order to achieve superior MEA plat lnw loading reproducibility. To make highly viscous catalyst slurry that is imperative for using coater, we use 40wt.% Nafion solution and minimize the content of organic solvent. And the choice of proper high surface area catalyst is important in the viewpoint of making well-dispersed slurry. After catalyst coating onto the support material, we transferred the catalyst layer to both sides of Nafion membrane by hot-pressing In this case, the degree of transfer was Influenced by hot-pressing condition including temperature, pressure, and time. To compare the transferring ability, we compared so many films and detaching papers. And among the support, polyethylene terephthalate(PET) film shows the prominent result.

• 한국전기화학회:학술대회논문집
• /
• 2005.04a
• /
• pp.59-59
• /
• 2005

• Transactions of the Korean hydrogen and new energy society
• /
• v.23 no.3
• /
• pp.256-263
• /
• 2012

We studied the degradation phenomenon of Pt catalyst in PEMFC. We used the electron microscope analysis technique including the ultra-microtome pretreatment method, FEG-SEM and TEM analysis methods for analysis of Pt nanoparticles. The Pt catalyst degradation is observed not only in electrode site but also in membrane site. We investigated these various degradation phenomena. The cathode electrode layer thickness is reduced. The size of the catalyst is increased much larger than initial size in membrane site. The catalyst moved from electrode layer to the electrolyte membrane. The rounded shape of catalyst was changed to the polygon. As a result, we found that the catalyst degradation processes of migration and coarsening occurred by the followings mechanisms; (1) dissolution of Pt ; (2) diffusion of Pt ion ; (3) Pt ion chemical reduction in membrane; (4) Coarsening of Pt particles (Ostwald ripening) ; (5) polygon shape change of Pt by {111} plane growth.

• Clean Technology
• /
• v.13 no.4
• /
• pp.293-299
• /
• 2007

Direct coating of catalyst layer on the $Nafion^{(R)}$ membrane has been optimized in the process of fabrication of membrane electrode assembly (MEA) to enhance the performance of direct methanol fuel cell (DMFC). In this method, the contact resistance at the interface of the catalyst layer and the membrane was found to be low. The effect of catalyst loading, thickness of membrane and the gas diffusion layer (GDL) with or without the presence of micro-porous layer (MPL) on the performance of the MEA was also investigated. The MEA fabricated by the above-mentioned method exhibited a performance of $147\;mW/cm^2$ and $100\;mW/cm^2$ at $80^{\circ}C$ and $60^{\circ}C$, respectively, with the catalysts loading of $4\;mg/cm^2$.

• Journal of the Korean Electrochemical Society
• /
• v.2 no.4
• /
• pp.190-194
• /
• 1999

Etched Nafion membrane and electrode assemblies were fabricated and those performances were observed in PEMFC. Adhesion of membrane to electrode increased with abrasion of membrane surface. Membrane surface ething results in reduction of hot pressing temperature, as a consequence, in improving of cell performance. It was found that Nafion etching was effective in painting method. The optimum content of electrode catalyst should be selected according to etching intensity.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.10a
• /
• pp.37-39
• /
• 2008

본 연구에서는 저온 데칼 전사법을 이용하여 막 전극 접합체(Membrane Electrode Assembly, MEA)를 제조하였다. 제조된 MEA는 직접 메탄올 연료 전지(Direct Methanol Fuel Cell, DMFC)를 이용하여 성능 테스트를 하였다. 저온 데칼 전사법은 $140^{\circ}C$의 낮은 온도에서 촉매 층을 데칼 기판에서 멤브레인으로 전사시키고, 전사된 촉매 층의 표면에 형성되는 것으로 알려진 이오노머 스킨 층의 형성을 막기 위해 이오노머/촉매/카본/기판의 구조로 되어 있는 데칼 기판을 사용한다. 저온 데칼 전사법으로 제조 된 카본 층이 있는 MEA의 DMFC 성능이 카본 층이 없이 데칼 전사법으로 제조된 MEA나 전통적인 고온 데칼 전사법으로 제조된 MEA, 또는 직접 스프레이 코팅법으로 제조된 MEA의 성능보다 높게 나온 것을 알 수 있다. 저온 데칼 전사법으로 제조된 MEA의 DMFC 성능이 향상된 것은 촉매 층 위에 이오노머 스킨이 형성되지 않아 반응물의 확산이 원활하게 이루어지기 때문이다. 이를 위한 특성 분석으로 EIS, CV를 측정하였다.