직접메탄올연료전지에서 메탄올 크로스오버에 미치는 인자 연구

현민수,김상경,임성엽,이병록,백동현,정두환,Hyun, Min-Soo,Kim, Sang-Kyung,Lim, Seong-Yop,Lee, Byung-Rock,Peck, Dong-Hyun,Jung, Doo-Hwan 한국전기화학회 2008 한국전기화학회지 Vol.11 No.1

직접메탄올연료전지의 운전 변수에 따른 메탄올 크로스오버를 메탄올 농도센서를 이용하여 정량적으로 측정하였으며 실제 셀 운전 시 메탄올크로스오버 저감의 측면에서 유리한 운전조건을 분석하였다. 메탄올 농도, 전극 양단의 압력차, 전류의 크기, 온도, stoichiometry등을 변화시켜 diffusion, convection, electro-osmosis의 메커니즘별 기여도와 실제 전지 운전 조건의 영향을 함께 분석하였다. 이상의 세 가지 메커니즘 중에서 농도 차이에 의한 diffusion이 가장 큰 영향을 미쳤으며 electro-osmosis에 의한 영향은 고농도에서만 관찰할 수 있었다. The amount of methanol crossover was measured with changing the operating condition by using a liquid methanol concentration sensor. Appropriate operating condition was discussed in terms of methanol crossover. Mechanism of methanol crossover was classified into three items which are diffusion, convection and electro-osmosis. Contribution of each mechanism to methanol crossover and the effect of operating condition were analyzed with varying methanol concentration, pressure difference between anode and cathode, current, temperature, and stoichiometry of anode fuel. Among the three mechanisms diffusion affected mostly and electro-osmosis effect was observed only under high methanol concentration.

Development of an advanced MEA to use high-concentration methanol fuel in a direct methanol fuel cell system

Kang, K.,Lee, G.,Gwak, G.,Choi, Y.,Ju, H. Pergamon Press ; Elsevier Science Ltd 2012 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.37 No.7

Despite serious methanol crossover issues in Direct Methanol Fuel Cells (DMFCs), the use of high-concentration methanol fuel is highly demanded to improve the energy density of passive fuel DMFC systems for portable applications. In this paper, the effects of a hydrophobic anode micro-porous layer (MPL) and cathode air humidification are experimentally studied as a function of the methanol-feed concentration. It is found in polarization tests that the anode MPL dramatically influences cell performance, positively under high-concentration methanol-feed but negatively under low-concentration methanol-feed, which indicates that methanol transport in the anode is considerably altered by the presence of the anode MPL. In addition, the experimental data show that cathode air humidification has a beneficial effect on cell performance due to the enhanced backflow of water from the cathode to the anode and the subsequent dilution of the methanol concentration in the anode catalyst layer. Using an advanced membrane electrode assembly (MEA) with the anode MPL and cathode air humidification, we report that the maximum power density of 78 mW/cm<SUP>2</SUP> is achieved at a methanol-feed concentration of 8 M and cell operating temperature of 60 <SUP>o</SUP>C. This paper illustrates that the anode MPL and cathode air humidification are key factors to successfully operate a DMFC with high-concentration methanol fuel.

Simulation and Validation of Methanol Crossover in DMFCs

고요한(Ko, Johan),주현철(Ju, Hyunchul) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.06

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.

Self-Assembly Modification of Perfluorosulfonic Acid Membranes for the Application to Direct Methanol Fuel Cells

문고영,임지원 한국고분자학회 2008 Macromolecular Research Vol.16 No.6

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.

Effects of the Operating Conditions on the Performance of Direct Methanol Fuel Cells

한창화,김남훈,이중희 한국수소및신에너지학회 2011 한국수소 및 신에너지학회논문집 Vol.22 No.3

This study examines the effects of the ambient temperature (AT), methanol feeding temperature (MFT), methanol concentration (MC) and methanol flow rate (MFR) on the performance and cell temperature (CT) of a 5-stacked direct methanol fuel cell (DMFC). The AT, MFT, MC, and MFR are varied from -10°C to +40°C, 50°C to 90°C, 0.5M to 3.0M and 11.7 mL min^-1 to 46.8 mL min^-1, respectively. The performance of the DMFC under various operating conditions is analyzed from the I-V polarization curve, and the methanol crossover is estimated by gas chromatography (GC). The performance of the DMFC improves significantly with increasing AT. The open circuit voltage (OCV) decreases with increasing MC due to the enhanced likelihood of methanol crossover. The cell performance is improved significantly when the MFR is increased from 11.7 mL min^-1 to 28.08 mL min^-1. The change in cell performance is marginal with further increases in MFR. The CT increases significantly with increasing AT. The effect of the MFT and MFR is moderate, and the effect of MC is marginal on the CT of the DMFC.

Self-Assembly Modification of Perfluorosulfonic Acid Membranes for the Application to Direct Methanol Fuel Cells

Moon, Go-Young,Rhim, Ji-Won The Polymer Society of Korea 2008 Macromolecular Research Vol.16 No.6

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.

A hierarchical cathode catalyst layer architecture for improving the performance of direct methanol fuel cell

Kim, Sungjun,Park, Ji Eun,Hwang, Wonchan,Cho, Yong-Hun,Sung, Yung-Eun Elsevier BV 2017 Applied Catalysis B Vol.209 No.-

<P><B>Abstract</B></P> <P>We report the fabrication of a hierarchical cathode catalyst layer (CL) for application in direct methanol fuel cells (DMFCs). The hierarchical CL, comprised of Pt black as the inner layer and Pt/C as the outer layer, has appropriate structural properties for DMFC cathode. The inner CL with compact structure decreases the CL thickness and prevent Pt sites from methanol contamination, and the cathode outer CL with porous structure increase the electrochemical active surface area. Consequently, the hierarchical cathode CL is able to offset the adverse effect of methanol crossover on the cathode performance by enhancing the Pt catalyst utilization for oxygen reduction reactions (ORR). Therefore, the newly developed membrane electrode assembly (MEA) can maintain the high ORR activity of the cathode catalysts despite the methanol crossover. At a high methanol concentration (3M), it shows high maximum power density (0.156Wcm<SUP>−2</SUP>) despite only 1.0mgcm<SUP>−2</SUP> of Pt in the cathode CL.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel MEA with hierarchical cathode catalyst layer (CL) is proposed. </LI> <LI> The MEA shows outstanding DMFC performance despite low Pt loading (1.0mgcm<SUP>−2</SUP>). </LI> <LI> The MEA can maintain the high ORR activity of cathode despite the methanol crossover. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

DC마그네트론 스퍼터링으로 Pd박막 입힌 Nafion막의 특성

황기호,조원일,조병원,윤성렬,하흥용,오인환,김광범,Hwang, Gi-Ho,Cho, Won-Il,Cho, Byung-Won,Yoon, Sung-Ryul,Ha, Heung-Yong,Oh, In-Hwan,Kim, Kwang-Bum 한국전기화학회 2002 한국전기화학회지 Vol.5 No.2

상용 고분자 전해질인 Nafion 115 및 Nafion 117막 위에 do magnetron sputtering방법으로 Pd박막을 다양한 두께로 증착한 다음, 개질된 고분자 전해질 막의 morphology, proton 전도도(conductivity), 메탄을 투과도(permeability)를 측정하였으며, membrane and electrode assemblies(MEA)를 구성하여 DMFC 단위전지 성능을 측정하였다. Pd 박막은 Nafion막이 지니고 있는 단점인 메탄을 crossover에 대한 barrier로서 작용하였지만, 동시에 Nafion막의 고유 특성인 proton전도도의 감소를 가져왔다. Pd박막에 의하여 개질된 Nafion막의 메탄올에 대한 투과도와 proton전도도는 Nafion 막 상에 증착된 Pd 박막의 두께가 증가할수록 직선적으로 감소하는 경향을 나타냈다 개질된 Nafon 막을 사용하여 제작한 direct methanol fuel cell(DMFC)단위전지의 성능은 전체적으로 약간 저하되었다. 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.

휴대전원용 직접 알코올 연료전지의 특성에 관한 연구

윤성렬,차석열,오인환,홍성안,하흥용,Yoon S. R.,Cha S. Y.,Oh I. W.,Hong S. A.,Ha H. Y. 한국전기화학회 2001 한국전기화학회지 Vol.4 No.2

상온$\cdot$상압에서 운전되는 휴대전원용 연료전지 시스템에서 연료에 따른 애노드와 캐소드의 전위특성과 알코올 크로스오버의 영향 및 운전에 적합한 알코올 연료의 농도를 확인한 결과, 고분자 전해질 막을 통한 액상연료의 크로스오버는 메탄올, 에탄올, 그리고 이소프로필 알코올 모두에서 발생하였고, 고정형 연료시스템을 적용한 단위전지의 성능은 4.5 M의 메탄올이 0.23V에서 $31mW/cm^2$로 가장 우수하였다. 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.

A study on the overall efficiency of direct methanol fuel cell by methanol crossover current

Seo, Sang Hern,Lee, Chang Sik Elsevier 2010 APPLIED ENERGY Vol.87 No.8

<P><B>Abstract</B></P><P>This paper was presented to determine the methanol crossover and efficiency of a direct methanol fuel cell (DMFC) under various operating conditions such as cell temperature, methanol concentration, methanol flow rate, cathode flow rate, and cathode backpressure. The methanol crossover measurements were performed by measuring crossover current density at an open circuit using humidified nitrogen instead of air at the cathode and applied voltage with a power supply. The membrane electrode assembly (MEA) with an active area of 5cm<SUP>2</SUP> was composed of a Nafion 117 membrane, a Pt–Ru (4mg/cm<SUP>2</SUP>) anode catalyst, and a Pt (4mg/cm<SUP>2</SUP>) cathode catalyst. It was shown that methanol crossover increased by increasing cell temperature, methanol concentration, methanol flow rate, cathode flow rate and decreasing cathode backpressure. Also, it was revealed that the efficiency of the DMFC was closely related with methanol crossover, and significantly improved as the cell temperature and cathode backpressure increased and methanol concentration decreased.</P>