Membrane electrode assembly polymer

Polymer Electrolyte Fuel Cells, Membrane-Electrode Assemblies > Polymer Electrolyte Fuel Cells, Perfluorinated Membranes... 

Bose, A. B., Shaik, R., and Mawdsley, J. Optimization of the performance of polymer electrolyte fuel cell membrane electrode assemblies Roles of curing parameters on the catalyst and ionomer structures and morphology. Journal of Power Sources 2008 182 61-65. 

Hoshi, N., Uematsu, N., Saito, H., Hattori, M., Aoyagi, T. and Ikeda, M. 2005. Membrane electrode assembly for polymer electrolyte fuel cell. US Patent 2005130006. 

Endo, E., Terasono, S. and Haidiyanto, W. 2004. Solid polymer electrolyte membrane and membrane electrode assembly for solid polymer fuel cell. Japan Patent 2004247155. 

Figure 4.1 shows a schematic of a typical polymer electrolyte membrane fuel cell (PEMFC). A typical membrane electrode assembly (MEA) consists of a proton exchange membrane that is in contact with a cathode catalyst layer (CL) on one side and an anode CL on the other side they are sandwiched together between two diffusion layers (DLs). These layers are usually treated (coated) with a hydrophobic agent such as polytetrafluoroethylene (PTFE) in order to improve the water removal within the DL and the fuel cell. It is also common to have a catalyst-backing layer or microporous layer (MPL) between the CL and DL. Usually, bipolar plates with flow field (FF) channels are located on each side of the MFA in order to transport reactants to the... 

T. Erey and M. Linardi. Effects of membrane electrode assembly preparation on the polymer electrolyte membrane fuel cell performance. Electrochimica Acta 50 (2004) 99-105. 

A.Z. Weber, M.A. Hickner, Modeling and high-resolution-imaging studies of water-content profiles in a polymer-electrolyte-fuel-cell membrane-electrode assembly. Electrochimica. Acta. 53, 7668—7674 (2008)... 

Figure 3.15. Schematic representation of the correlation between fuel cell impedance and polarization curve. (Modified from [23], with kind permission from Springer Science+Business Media Journal of Applied Electrochemistry, Characterization of membrane electrode assemblies in polymer electrolyte fuel cells using a.c. impedance spectroscopy, 32(8), 2002, 859-63, Wagner N. Figure 4.)...

Wagner N (2002) Characterization of membrane electrode assemblies in polymer electrolyte fuel cells using a.c. impedance spectroscopy. J Appl Electrochem 32(8) 859-63... 

Clearly, a fundamental understanding of the key strac-ture/property relationships, particularly membrane morphology and conductivity as a function of polymer electrolyte architecture and water content - both in the bulk hydrated membrane and at the various interfaces within the membrane electrode assembly (MEA), can provide guidance in the synthesis of novel materials or MEA manufacturing techniques that lead to the improvement in the efficiency and/or operating range of PEMFCs. 

Figure 1. From the macroscale to the nanoscale a membrane electrode assembly has a polymer electrolyte membrane sandwiched between two catalyst layers and gas diffusion layers. The catalyst layer is composed of carbon particles impregnated with catalyst nanoparticles. Effective utilization of the catalyst particles depends on their local environment.

A publication by the Paul Scherrer Institute reports progress in preparing membrane/electrode assemblies for polymer electrolyte fuel cells based on radiation-grafted FEP PSSA membranes [95]. Hot-pressing with Nation was used to improve the interfaces. These improved MEAs showed performance data comparable to those of MEAs based on Nafion 112 (Figure 27.58) and an service-life in H2/O2 fuel cells of more than 200 h at 60°C and 500 mA cm. ... 

P. Millet, J. Alleau and R. Durand, Characteristics of membrane-electrode assemblies for solid polymer electrolyte water electrolysis, J. Appl. Electrochem., 1993, 23, 322. 

Recently, taking advantage of the very narrow size distribution of the metal particles obtained, microemulsion has been used to prepare electrocatalysts for polymer electrolyte membrane fuel cells (PEMFCs) Catalysts containing 40 % Pt Ru (1 1) and 40% Pt Pd (1 1) on charcoal were prepared by mixing aqueous solutions of chloroplatinic acid, ruthenium chloride and palladium chloride with Berol 050 as surfactant in iso-octane. Reduction of the metal salts was complete after addition of hydrazine. In order to support the particles, the microemulsion was destabilised with tetrahydrofurane in the presence of charcoal. Both isolated particles in the range of 2-5 nm and aggregates of about 20 nm were detected by transmission electron microscopy. The electrochemical performance of membrane electrode assemblies, MEAs, prepared using this catalyst was comparable to that of the MEAs prepared with a commercial catalyst. 

In experiments, we used an ion-exchange membrane made of MF-4SK (Nafion-type) perfluorinated polymer with functional sulfo-groups for preparation of membrane-electrode assemblies (MEAs). The membrane thickness was 130 Xm, the exchange capacity was 0.86 mg-equiv/g, the catalyst was 20 wt % Pt on a hydrophobic carbon carrier, the catalyst loading at the anode and cathode was 0.35 mg/cm. ... 

Solutions of DMM, TMM and methanol were evaluated in single cells and a 5-cell stack supplied by Giner, Inc. The cells were operated at temperatures ranging from 25 °C to 90 °C and were heated at the ceil block and the anode fuel reservoir, which was equipped with a condenser to prevent evaporation but allow CO2 rejection from the system. In the present study, the membrane electrode assembly (manufactured by Giner Inc.) consisted of electrocatalytic Pt-Ru (50/50 atom %) and R fine metal powders (surface area 30-70 m /g) bonded to either side of a Nafion -117 polymer electrolyte membrane. The... 

The proton exchange membrane - also known as polymer electrolyte membrane (PEM) - fuel cell uses a polymeric electrolyte. The protonconducting polymer forms the heart of each cell electrodes, usually made of porous carbon with catalytic platinum incorporated into them, are bonded to either side of the electrolyte to form a one-piece membrane-electrode assembly (MEA). The following are some key advantages that make PEMs such a promising technology for the automotive market ... 

After extended operation of an STR PEM fuel cell with the same membrane electrode assembly (> 2500 h), autonomous oscillations were observed under conditions where the STR PEM fuel cell exhibited 5 steady states [23]. An example of the oscillations is shown in Figure 3.11.These oscillations have periods of 10 -10 s and show characteristics of a capacitively coupled switch. The oscillations transition very rapidly (<10s) between high and low states with an overshoot on the rise and undershoot and recovery on the fall. The period, magnitude and on/off times for these oscillations varied with temperature, and load resistance. Benziger and co-workers have suggested that these unusual dynamics are associated with mechanical relaxations of the polymer membrane driven by changing water content, but the detailed physical processes causing these unusual dynamics are not yet understood. 

A typical cross section of a polymer electrolyte fuel cell (PEFQ is sketched in Figure 6.1. The membrane electrode assembly (MEA) is clamped between two metal or graphite plates with the channels for feed gases supply, called the flow field . The MEA usually consists of two gas-diffusion layers (GDLs) and two catalyst layers, separated by proton-conducting membrane. 

Fig. 3 Components of the polymer electrolyte fuel cell (PEFC) membrane electrode assembly (MEA) on the left, including separator plates and gasket. A schematic of a PEFC stack is shown on the right, comprising a number of single cells in series...

This introductory chapter provides a brief outline and history of the PEFC technology, and important requirements and aspects in the development of polymer membranes for fuel cells. To obtain materials that meet specific requirements, the relationship of composition/structure and the properties has to be estabUshed. For the preparation of the membrane electrode assembly, it is important to understand the interfacial properties between membrane and electrodes. 

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