Development of a novel hydrophobic/hydrophilic double micro porous layer for use in a cathode gas diffusion layer in PEMFC

Chun, J.H.,Park, K.T.,Jo, D.H.,Lee, J.Y.,Kim, S.G.,Park, S.H.,Lee, E.S.,Jyoung, J.Y.,Kim, S.H. Pergamon Press ; Elsevier Science Ltd 2011 International journal of hydrogen energy Vol.36 No.14

In this study, a gas diffusion layer (GDL) was modified to improve the water management ability of a proton exchange membrane fuel cell (PEMFC). We developed a novel hydrophobic/hydrophilic double micro porous layer (MPL) that was coated on a gas diffusion backing layer (GDBL). The water management properties, vapor and water permeability, of the GDL were measured and the performance of single cells was evaluated under two different humidification conditions, R.H. 100% and 50%. The modified GDL, which contained a hydrophilic MPL in the middle of the GDL and a hydrophobic MPL on the surface, performed better than the conventional GDL, which contained only a single hydrophobic MPL, regardless of humidity, where the performance of the single cell was significantly improved under the low humidification condition. The hydrophilic MPL, which was in the middle of the modified GDL, was shown to act as an internal humidifier due to its water absorption ability as assessed by measuring the vapor and water permeability of this layer.

Electrospray-assisted fabrication of porous platinum-carbon composite thin layers for enhancing the electrochemical performance of proton-exchange membrane fuel cells

Nian Shan,정훈,안지영,김지훈,김수형 한국물리학회 2018 Current Applied Physics Vol.18 No.6

Membrane electrode assembly (MEA) in proton-exchange membrane fuel cells (PEMFCs) have been fabricated using electrospray-assisted deposition of platinum-carbon composites on carbon-fiber-based paper substrate, because the technique is versatile, operated in atmospheric pressure, and easy to scale up for commercialization. In this study, we investigate the effects of electrospray-assisted platinum loadings from 0.1 to 0.5 mg cm−2 on the electrochemical performance of PEMFCs. The PEMFCs with platinum loading of 0.3 mg cm−2 generate the highest power density, which is ∼35% higher than that of PEMFCs fabricated by traditional brush-deposited catalyst layers. Relatively high platinum loading (>0.3 mg cm−2) enhances the pressure drop in MEA; therefore, the resulting power density is decreased due to low-reacting gas permeability. We also examine the effect of porous structures on the electrochemical performance of PEMFCs. Brij 58-based surfactant templates create micro- and nano-porous structures in the platinum-carbon composite thin layers via thermal removal. These porous structures in the platinum-carbon composite thin layers increase the reacting gas permeability and simultaneously lower the cell resistance, significantly enhancing the electrochemical performance of PEMFCs with porous structures.

고분자전해질 연료전지에서 다양한 기체확산층의 물리적 특성과 연료전지 성능 비교

이지정,김인태,장언,이홍기,심중표,Lee, Ji-Jung,Kim, In-Tae,Zhang, Yan,Lee, Hong-Ki,Shim, Joong-Pyo 한국전기화학회 2007 한국전기화학회지 Vol.10 No.4

다양한 종류의 기체확산층 (gas diffusion layer, GDL)을 이용하여 고분자전해질 연료전지의 성능을 시험하였으며 이를 통해 GDL의 물리적 특성과 연료전지의 성능과의 상관관계를 규명하고자 하였다. 전기전도도, 기공도, air permeability, water flux, PTFE 함량, micro-porous layer (MPL)의 유무에 따른 연료전지 성능의 변화가 고찰되었다. GDL의 물리적 특성들은 서로 밀접한 관계를 가지고 있어 연료전지의 성능변화에 영향을 주었다. Carbon paper나 carbon cloth상에 MPL의 형성이 GDL의 물리적 특성을 변화시켜 연료전지의 성능을 변화시킬 수 있음을 관찰하였다. 물리적 특성과 연료전지 성능과의 관계는 전류밀도의 크기에 따라 다른 경향을 나타내거나 혹은 무관한 경향을 보였다. PEMFC electrodes with various gas diffusion layers (GDL) were characterized to find out the effect of GDL on fuel cell performance. The physical properties of GDL such as electric conductivity, porosity, air permeability, water flux, PTFE content, etc had close relationship each other and affected on the variation of the cell performance. It was observed that the micro-porous layer (MPL) on carbon paper or cloth changed the physical properties of GDL and changed the cell performance. The variation of cell performance as a function of the physical properties of GDL showed different behaviors according to the amount of current density.

Improving the cold-start capability of polymer electrolyte fuel cells (PEFCs) by using a dual-function micro-porous layer (MPL): Numerical simulations

Ko, J.,Kim, W.G.,Lim, Y.D.,Ju, H. Pergamon Press ; Elsevier Science Ltd 2013 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.38 No.1

A novel micro-porous layer (MPL) is designed to enhance the cold-start capability of a polymer electrolyte fuel cell (PEFC). The concept of designing an MPL is to expand the ice storage capacity of the electrode into the MPL region. We impose proton conduction capability and the oxygen reduction reaction (ORR) kinetic activity on the MPL via controlling the platinum (Pt) loading, ionomer fraction and weight ratio of Pt to the carbon support (wt%<SUB>Pt-C</SUB>) of the MPL. Therefore, the MPL is dual-functional, and can work as a typical MPL for normal PEFC operations and as a part of the cathode catalyst layer (CL) for cold-start operations. Three-dimensional (3-D) cold-start simulations are carried out by using a 3-D cold-start model developed in a previous study [1]. The detailed simulation results clearly suggest that the cold-start operational time can be extended significantly using a dual-function MPL, and the extended time is directly proportional to the pore volume of the MPL for ice storage. This study provides a new strategy to enhance the cold-start capability of a PEFC by properly designing and optimizing the MPL.

Analytical solution for buckling analysis of micro sandwich hollow circular plate

Mohammad Mousavi,Mehdi Mohammadimehr,Rasoul Rostami 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.24 No.3

In this paper, the buckling of micro sandwich hollow circular plate is investigated with the consideration of the porous core and piezoelectric layer reinforced by functionally graded (FG)carbon nano-tube. For modeling the displacement field of sandwich hollow circular plate, the high-order shear deformation theory (HSDT) of plate and modified couple stress theory (MCST) are used. The governing differential equations of the system can be derived using the principle of minimum potential energy and Maxwell’s equation that for solving these equations, the Ritz method is employed. The results of this research indicate the influence of various parameters such as porous coefficients, small length scale parameter, distribution of carbon nano-tube in piezoelectric layers and temperature on critical buckling load. The purpose of this research is to show the effect of physical parameters on the critical buckling load of micro sandwich plate and then optimize these parameters to design structures with the best efficiency. The results of this research can be used for optimization of micro-structures and manufacturing different structure in aircraft and aerospace.

Analysis of the transient response and durability characteristics of a proton exchange membrane fuel cell with different micro-porous layer penetration thicknesses

Cho, J.,Park, J.,Oh, H.,Min, K.,Lee, E.,Jyoung, J.Y. Applied Science Publishers 2013 APPLIED ENERGY Vol.111 No.-

The optimal design of the gas diffusion layer (GDL) of proton exchange membrane fuel cells is crucial because it directly determines the mass transport mechanism of the reactants and products. In this study, the micro-porous layer (MPL) penetration thickness, which affects the pore size profile through the GDL, is varied as the design parameter of the GDL. The cell performance is investigated under various humidity conditions, and the water permeability characteristics are studied. In addition, the accelerated carbon corrosion stress test is conducted to determine the effect of MPL penetration on GDL degradation. GDLs with large MPL penetration thickness show better performance in the high-current-density region due to the enhanced management of water resulting from a balanced capillary pressure gradient. However, the loss of penetrated MPL parts is observed due to the low binding force between the MPL and the GDL substrate.

고분자전행질형 연료전지내 마이크로다공층 영향에 대한 수치적 연구

강경문(Kyungmun Kang),주현철(Hyunchul Ju) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11

In the fuel cell community it is well-known that a micro-porous layer (MPL) plays a crucial role in the water management of polymer electrolyte fuel cells (PEFCs), and thereby, significantly stabilizes and improves cell performance. In this paper, a numerical MPL model is developed and embodied with comprehensive, multi-dimensional, multi-phase fuel cell models that were developed earlier to discover the exact roles of MPLs,. The effects of different porous properties and liquid-entry pressures between an MPL and a gas diffusion layer (GDL) are examined via fully three-dimensional numerical simulations. Discontinuity in liquid saturation at the GDL/MPL interface is captured by the model when the differences in pore properties and wettability between the MPL and GDL are taken into account without considering variation in the liquid-entry pressures. However, the simulation of this case fails to capture the beneficial effects of an MPL on cell performance, predicting even lower performance than the case of no MPL. On the other hand, when a high liquid-entry pressure in an MPL is additionally considered, the numerical MPL model predicts liquid-free MPL and successfully demonstrates the phenomenon that the high liquid-entry pressure of the MPL prevents any liquid water from entering the MPL. Consequently, it is found from the simulation results that the liquid-free MPL significantly enhances the back-flow of water across the membrane into the anode, which, in turn, helps to avoid membrane dehydration and alleviate the level of GDL flooding. As a result, the model successfully reports the beneficial effects of MPLs on PEFC performance and predicts higher performance in the presence of MPLs (e.g., an increase of 67 ㎷ at 1.5 A ㎝-2). This study provides a fundamental explanation for MPL functions and quantifies the influence of MPL’s porous properties and the liquid-entry pressure on water transport and cell performance.

Determination of the pore size distribution of micro porous layer in PEMFC using pore forming agents under various drying conditions

Chun, J.H.,Park, K.T.,Jo, D.H.,Lee, J.Y.,Kim, S.G.,Lee, E.S.,Jyoung, J.Y.,Kim, S.H. Pergamon Press ; Elsevier Science Ltd 2010 International journal of hydrogen energy Vol.35 No.20

In this paper, the effect of the pore size distribution of a micro-porous layer (MPL) on the performance of polymer electrolyte membrane fuel cells (PEMFC) was investigated using self-made gas diffusion layers (GDLs) with different MPLs for which the pore size distribution was modified using pore forming agents under different drying conditions. When MPL dried at high temperature, more macro pores, approximately 1,000-20,000 nm in diameter, and less micro pores, below 100 nm, were observed relative to when MPL was dried at low temperature. Self-made GDLs were characterized by a field-emission scanning electron microscope (FE-SEM), mercury porosimetry and self-made gas permeability measurement equipment. The performance of the single cells was measured under two different humidification conditions. The results demonstrate that the optimum pore size distribution of MPL depended on the cell operating humidification condition. The MPL dried at high temperature performed better than the MPL dried at low temperature under a low humidification condition; however, MPL dried at low temperature performed better under a high humidification condition.

Effects of the microstructure and powder compositions of a micro-porous layer for the anode on the performance of high concentration methanol fuel cell

Kim, Y.S.,Peck, D.H.,Kim, S.K.,Jung, D.H.,Lim, S.,Kim, S.H. Pergamon Press ; Elsevier Science Ltd 2013 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.38 No.17

To investigate the effects of the microstructure and powder compositions for the micro-porous layer (MPL) of an anode on the cell performance of a direct methanol fuel cell (DMFC) using a highly concentrated methanol solution up to 7 M, various powders and their compositions were applied as a filler of the MPL in the membrane electrode assembly (MEA). Several nano- and microstructured carbons such as commercial carbon black (CB), spherical activated carbon (AC), multi-walled carbon nanotube (MWCNT), and platelet carbon nanofiber (PCNF) were selected with different morphology and surface properties, and a meso-porous silica (one of SBA series) was also included for its porous and hydrophilic properties. The coating morphology and physical properties such as porosity and gas permeability were measured, and electrochemical properties of MEA with the MPL were examined by using current-voltage polarization, electrochemical impedance spectroscopy, and voltammetric analyses. A mixture of different carbons was found to be effective for lowering methanol crossover with sustaining electrical conductivity and gas permeability. A MEA with modified-anode MPLs made of CB (50 vol%) and PCNF (50 vol%) powders showed a maximum power density of 67.7 mW cm<SUP>-2</SUP> under operation with a 7 M concentration of methanol.

Experimental dissection of oxygen transport resistance in the components of a polymer electrolyte membrane fuel cell

Oh, Hwanyeong,Lee, Yoo il,Lee, Guesang,Min, Kyoungdoug,Yi, Jung S. Elsevier 2017 Journal of Power Sources Vol.345 No.-

<P><B>Abstract</B></P> <P>Oxygen transport resistance is a major obstacle for obtaining high performance in a polymer electrolyte membrane fuel cell (PEMFC). To distinguish the major components that inhibit oxygen transport, an experimental method is established to dissect the oxygen transport resistance of the components of the PEMFC, such as the substrate, micro-porous layer (MPL), catalyst layer, and ionomer film. The Knudsen numbers are calculated to determine the types of diffusion mechanisms at each layer by measuring the pore sizes with either mercury porosimetry or BET analysis. At the under-saturated condition where condensation is mostly absent, the molecular diffusion resistance is dissected by changing the type of inert gas, and ionomer film permeation is separated by varying the inlet gas humidity. Moreover, the presence of the MPL and the variability of the substrate thickness allow the oxygen transport resistance at each component of a PEMFC to be dissected. At a low relative humidity of 50% and lower, an ionomer film had the largest resistance, while the contribution of the MPL was largest for the other humidification conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Oxygen transport resistance is analyzed by measuring the limiting current density. </LI> <LI> Under/over-saturated regions are divided based on the resistance trend of the O<SUB>2</SUB>%. </LI> <LI> A strategy to dissect resistance with varying operating conditions is proposed. </LI> <LI> Resistance is dissected in Knudsen and molecular diffusions and permeation. </LI> <LI> Resistance is separated in each component of a PEMFC. </LI> </UL> </P>