• Journal of Electrochemical Science and Technology
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• 제13권3호
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• pp.354-361
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• 2022

In a direct methanol fuel cell system (DMFC), one of the drawbacks is methanol crossover. Methanol from the anode passes through the membrane and enters the cathode, causing mixed potential in the cell. Only Pt-based catalysts are capable of operating as cathode for oxygen reduction reaction (ORR) in a harsh acidic condition of DMFC. However, it causes mixed potential due to high activity toward methanol oxidation reaction of Pt. To overcome this situation, developing Pt-based catalyst that has methanol tolerance is significant, by controlling reactant adsorption or reaction kinetics. Pt/C decorated with phosphate ion was prepared by modified polyol method as cathode catalyst in DMFC. Phosphate ions, bonded to the carbon of Pt/C, surround free Pt surface and block only methanol adsorption on Pt, not oxygen. It leads to the suppression of methanol oxidation in an oxygen atmosphere, resulting in high DMFC performance compared to pristine Pt/C.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.583-584
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• 2012

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 C
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• pp.1252-1254
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• 1997

Direct methanol fuel cell based on a proton-exchange membrane electrolyte was investigated. 60% Pt-Ru/C and 60%Pt/C catalysts were employed for methanol oxidation and oxygen reduction, respectively. Morphologies of the catalysts were investigated by x-ray power diffraction, energy dispersive x-ray spectroscopy, and transmission microscopy. Electrochemical characteristics of the catalysts were tested by using cyclic voltametry technique. I-V characteristics of the fuel cell were tested by changing methanol concentration, temperature, and Nafion type as a proton-exchange membrane electrolyte. AC impedance technique was used to investigate the electrochemical performance of the fuel cell. The performance of single cell was enhance with increasing cell temperature. High operation temperature attributed to the combined effects of the reduction of ohmic resistance and polarization. High cell voltage was obtained from the concentration of 205M methanol. With Nafion 112, a current density of $230mA/cm^2$ at 0.55V was obtained from the concentration of 2.5M methanol.

• Macromolecular Research
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• 제14권4호
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• pp.449-455
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• 2006

Ionic cluster mimic, polymer electrolyte membranes were prepared using polymer composites of crosslinked poly(vinyl alcohol) (PVA) with sulfated-${\beta}$-cyclodextrins (${\beta}-CDSO_3H$) or phosphated-${\beta}$-cyclodextrins (${\beta}-CDPO(OH)_2$). When Nafion, developed for a fuel cell using low temperature, polymer electrolyte membranes, is used in a direct methanol fuel cell, it has a methanol crossover problem. The ionic inverted micellar structure formed by micro-segregation in Nafion, known as ionic cluster, is distorted in methanol aqueous solution, resulting in the significant transport of methanol through the membrane. While the ionic structure formed by the ionic sites in either ${\beta}-CDSO_3H$ or ${\beta}-CDPO(OH)_2$ in this composite membrane is maintained in methanol solution, it is expected to reduce methanol transport. Proton conductivity was found to increase in PVA membranes upon addition of ionized cyclodextrins. Methanol permeability through the PVA composite membrane containing cyclodextrins was lower than that of Nafion. It is thus concluded that the structure and fixation of ionic clusters are significant barriers to methanol crossover in direct methanol fuel cells.

• 전기화학회지
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• 제6권1호
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• pp.68-71
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• 2003

전지 성능을 저하시키지 않고 연료극 및 공기극의 귀금속 촉매량을 줄이기 위하여 다층막 전극을 이용한 직접메탄을 연료전지의 성능특성을 조사하였다. 다층막 전극 즉, 연료극과 공기극에 사용된 촉매사용량과 나피온 막의 종류를 변화시키며 최종성능을 측정하였다 본 실험에서 사용된 촉매량은 연료극이 $3-4mg/cm^2$ 공기극이 $1-2mg/cm^2$이다. 본 실험에서는 나피온 115를 사용한 MEA3의 $90^{\circ}C$, 2기압에서 측정 결과 최대 전력밀도인 $230mW/cm^2$를 나타내었다. 이 결과는 현재 시판되고 있는 상용전극과 거의 같은 수준의 성능을 보여주고 있는 반면, 금속 촉매의 양은 기존의 상용전극과 비교하여 약 $50\%$ 정도 감소된 것이다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.143.2-143.2
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• 2010

Therefore, with this development assignment we'd like to develop the hybrid system combining 800W DMFC (Direct Methanol Fuel Cell) and 1.6kW of Lithium secondary battery pack which can be applied to the most common small cart. a scooter, to secure the development capability of hundreds of Watts DMFC, the high-capacity Lithium secondary battery pack, the technology of BMS (Battery Management System) and the development technology of hybrid system. DMFC, in fact, has lower energy efficiency than PEMFC (Polymer Electrolyte Membrane Fuel Cell); however, it has several advantages in terms of fuel storage and use. It is pretty easy to be stored and used without any additional colling and heating devices because of its insensitive liquid methanol to temperature. In conclusion, DMFC system is the most suitable device for small mobile vehicles.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.126.1-126.1
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• 2010

In direct methanol fuel cells(DMFCs), it is well known that methanol crossover severely reduces the cell performance and the cell efficiency. There are a number of design and operating parameters that influence the methanol crossover. This indicates that a DMFC demands a high degree of optimization. For the successful design and operation of a DMFC system, a better understanding of methanol crossover phenomena is essential. The main objective of this study is to examine methanol-crossover phenomena in DMFCs. In this study, 1D DMFC model previously developed by Ko et al. is used. The simulation results were compared with methanol-crossover data that were measured by Eccarius et al. The numerical predictions agree well with the methanol crossover data and the model successfully captures key experimental trends.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1409-1411
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• 1996

Direct Methanol Fuel Cell(DMFC) using Pt-Ru electrocatlayst and Nafion menbrane can provide high performance if operating conditions are well designed. In this study, operating temperature, pressure, and fuel flow rate were changed to obtain optimum operating conditions of DHFC single cell. Performance of DMFC were increased by the increase of operating temperature. The concentration of fuel methanol was 2.0M $CH_{3}OH$ and pressure difference of cathode and anode was 2 atm were showed maximum performance of DMFC single cell with showing the current density of 160 $mA/cm^2$ at 0.2V cell voltage.

• Macromolecular Research
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• 제16권5호
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• pp.457-466
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• 2008

The relation between the phase separated morphologies and their transport properties in the polymer blend membrane for direct methanol fuel cell application was studied. In order to enhance the proton conductivity and reduce the methanol crossover, sulfonated poly(arylene ether sulfone) copolymer, with a sulfonation of 60 mol% (sPAES-60), was blended with nonsulfonated poly(ether sulfone) copolymer (RH-2000, Solvay). Various morphologies were obtained by varying the drying condition and the concentration of the casting solution (10, 15, 20 wt%). The transport properties of proton and methanol molecule through the polymer blend membranes were studied according to the absorbed water. AC impedance spectroscopy was used to measure the proton conductivity and a liquid permeability measuring instrument was designed to measure the methanol permeability. The state of water in the blend membranes was confirmed by differential scanning calorimetry and was used to correlate the morphology of the membrane with the membrane transport properties.

• 한국수소및신에너지학회논문집
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• 제23권3호
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• pp.243-249
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• 2012

A lightweight 200W direct methanol fuel cell (DMFC) stack is designed and fabricated to power a small scale Unmanned Aerial Vehicle (UAV). The DMFC stack consists of 33-cells in which membrane-electrode assemblies (MEAs) having an active area of 88 $cm^2$ are sandwiched with lightweight composite bipolar plates. The total stack weight is around 3.485 kg and stack performance is tested under various methanol feed concentrations. The DMFC stack delivers a maximum power of 248 W at 13.2 V and $71.3^{\circ}C$ under methanol feed concentration of 1.2 M. In addition, the voltage of individual cell in the 33-cell stack is measured at various current levels to ensure the stability of DMFC stack operations. The cell voltage distribution data exhibit the maximum cell voltage deviation of 28 mV at 15 A and hence the uniformity of cell voltages is acceptable. These results clearly demonstrate that DMFC technology becomes a potential candidate for small-scale UAV applications.