Membrane electrode assembly fabrication

New membrane materials for PEM fuel cells must be fabricated into a well-bonded, robust membrane electrode assembly (MEA) as depicted in Figure 1. In addition to the material requirements of the proton exchange membrane itself as outlined above, the ease of membrane electrode assembly fabrication and the resulting properties of the MEA are also... 

Advances in fuel cell technology over the last four decades have come primarily from improved electrocatalysts, membrane electrode assembly fabrication strategies, and cell/stack/system engineering. Apart from Nafion, new ion conducting polymeric materials have played only a minor role in significantly increasing cell performance. However, new materials... 

In experiments performed with different membrane-electrode-assembly fabrication techniques, and containing a PSSA-PVOF membrane with different properties than the ones previously discussed, the overall performance was similar to that previously obtained, as shown in Fig. 1.80. However the MEA tested displayed distinctly different behavior in contrast to samples previously discussed in that it showed less sensitivity to oxygen flow rate, as illustrated in Fig. 1.81. This behavior can partly be rationalized by increased methanol crossover rates observed for this MEA, which can contribute to aid in proper hydration of the cathode. However, since the increase in methanol crossover compared with the earlier samples is not dramatic ( 25% greater), other factors such as the concentration of sulfonic acid groups present at the membrane surface available for participation in the interfacial reaction zone as well as the concentration of perfluorocarbon binder contribute to produce conditions less sensitive to water management problems. 

Further improvements to membrane and membrane-electrode-assembly fabrication techniques resulted in cells with superior electrical performance to those previously tested, as shown in Fig. 1.100. In attempt to improve the... 

The identification of membrane properties relevant to fuel cells (ion exchange capacity, water uptake, conductivity), aspects of membrane electrode assembly fabrication, and fuel cell performance are described in detail in this review. 

The slurries of electro-catalysts were prepared by mixing together the catalysts and appropriate amount of 5wt % Nafion solution(Du Pont) including some kinds of dispersant[8]. The electrodes were made by spraying method with these well mixed inks. Two electrodes and Nafion 112 membrane were hot pressed with the condition of 50kgf/cm, 120°C for 3min to fabricate MEAs(Membrane Electrode Assembly). 

The membrane electrode assemblies (MEAs), in which the cathode was a commercial Pt/C catalyst (20 wt.%) with a Pt loading of 1.0 mg/cm, were fabricated by... 

Bender, G., Zawodzinski, T. A., and Saab, A. P. Fabrication of high-precision PEFG membrane electrode assemblies. Journal of Power Sources 2003 124 114—117. Ihm, J. W., Ryu, H., Bae, J. S., Ghoo, W. K., and Ghoi, D. K. High performance of electrode with low Pt loading prepared by simplified direct screen printing process in PEM fuel cells. Journal of Materials Science 2004 39 4647--4649. 

Kim, C. S., Ghun, Y. G., Peck, D. H., and Shin, D. R. A novel process to fabricate membrane electrode assemblies for proton exchange membrane fuel cells. International Journal of Hydrogen Energy 1998 23 1045-1048. 

Unlike the RDE technique, which is quite popular for characterizing catalyst activities, the gas diffusion electrode (GDE) technique is not commonly used by fuel cell researchers in an electrochemical half-cell configuration. The fabrication of a house-made GDE is similar to the preparation of a membrane electrode assembly (MEA). In this fabrication, Nation membrane disks are first hot-washed successively in nitric acid, sulphuric acid, hydrogen peroxide, and ultra-pure water. The membranes are then coated with a very thin active layer and hot-pressed onto the gas diffusion layer (GDL) to obtain a Nation membrane assembly. The GDL (e.g., Toray paper) is very thin and porous, and thus the associated diffusion limitation is small enough to be ignored, which makes it possible to study the specific kinetic behaviour of the active layer [6],... 

To build an efficient, high-quality microscale fuel cell, microfabrication techniques need to be combined with appropriate materials such as Nation based membrane electrode assemblies (MEAs). These techniques must be able to produce three-dimensional structures, allow reactant and product flow into and out of the device, process appropriate materials, and should be of low cost. Fortimately, traditional thin film techniques can be modified for microscale fuel cell fabrication, while maintaining their advantages of surface preparation, sensor integration, and finishing or packaging. In addition, other techniques are also available and are discussed in the following sections. 

Evaluate new membrane electrode assembly (MEA) fabrication protocols to enhance catalyst utilization and overall fuel cell efficiency. 

Develop new low-cost methods of fabricating membrane-electrode assemblies... 

Cyclic voltammetric studies indicated that the activity of the Pt-Ru films increased with operating temperature just as in conventional catalyst layers produced from unsupported catalyst inks. Membrane electrode assemblies were fabricated from Pt-Ru films of the most active compositions, and a power density of 800 mW/mg was realized for anodes that were deposited with about 0.1 mg/cm of Pt-Ru (see Figure 1). Applying the catalyst layers by sputter deposition on the electrode was found to yield better performance than applying them on the membrane. This was attributed to the enhanced electrical connectivity achieved when the catalyst layer is applied on the electrode. However, this is only true for very thin films. When thicker composite films are produced, such as those planned later in this project, good electrical connectivity may be achieved even with membrane deposition. 

Electrodes were fabricated with catalyst layers containing platinum-ruthenium alloys and platinum-ruthenium oxide. Membrane electrode assemblies were fabricated with such cells, and the performance was evaluated in a full cell configuration. Although ruthenium oxide is a proton conductor and is expected to enhance the rate of proton transport from the interface during methanol oxidation, no noticeable improvement in activity of the catalyst layer was observed by addition of ruthenium oxide. The role of other metal oxides such as tungsten oxide will be investigated next year, along with evaluation of non-noble metal catalysts based on nickel, titanium, and zirconium. 

Cooperatively fabricate and test membrane electrode assembly (MEAs) using the most promising membranes. This is to be done in partnership with an external company specializing in fuel cells. 

The PSSA-PVDF membranes were successfully fabricated into larger membrane electrode assemblies and tested in 2 x 2 (25 cm electrode area)... 

Mechanical integrity is one of the most important prerequisites for fuel cell membranes in terms of handhng and fabrication of membrane electrode assemblies, and to offer a durable material. Robust fuel cell membranes are required because of the presence of mechanical and swelling stresses in the application [172]. Moreover, membranes should possess some degree of elasticity or elongation to prevent crack formation. 

W.X. Kao, M.C. Lee, T.N. Lin, C.H. Wang, Y.C. Chang, and L.F Lin, A Novel Process for Fabrication of a Fully Dense Electrolyte Layer Embedded in a High Performance Membrane Electrode Assembly (MEA) (Unit Cell) of Solid Oxide Fuel Cell, EURO-Patent NO EP 2083465A1 (101-08-01). 

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