Recent Work on New Fuel Cell Membranes

Recent fuel cell membrane research and development (R D) efforts are summarized with a focus on (1) membranes for high-temperature, low-hmnidity PEMFC operation, (2) low-cost alternatives to PFSA membranes, and (3) direct methanol fuel cell membranes. A listing of fuel cell membrane performance data is given in Tables 29.4-29.6 for each membrane subcategory. The review material is by no means exhaustive, but it is representative of the kinds of fuel cell membranes previously/cmrently under investigation. For different viewpoints on the evolutionary development of various fuel cell membranes, the reader is directed to other review articles in the open hterature (Rikukawa and Sanui, 2000 Li et al., 2003 Haile, 2003 Jannasch, 2003 Savadogo, 2004 Hickner et al., 2004 Hogarth et al., 2005 Smitha et al., 2005). 

The membranes described here are designed to work in a hydrogen-air fuel ceU operating at a temperature of 100-200°C with minimal or no humidification of the reactant gases. 

1 AU-Polymeric Membranes—Immobilized Imidazole stem Presently, there is no purely polymeric membrane available with a sufficiently high proton conductivity ( 0.1 S/cm) for fuel cell operation under anhydrous or low water vapor pressure 

Microporous polyester filled with zirconium phosphate-sulphophenyl phosphonate Nafion - siUcotungstic acid 

Membrane thickness = 43 p.m, matrix Alberti et al. pore diameter = 0.8 p.m (2005) 

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Scale matters. We have seen that scale may be used to facilitate reconstruction of structures with nano-components, but it has also shown that scale is important when simulation takes place. When calculated correctly, properly, or if you like, usefully, transport effective coefficients can be determined and even compared to experimental data. However, in some cases new approaches may need to be considered. Here, approaches like mesoscopic physics, or a model of multiple scattering with effective media approximation (EMA) for condensed matter, based on the approach of atomic cluster, may play important roles. Recently, a review (Debe, 2012) was discussed on the different approaches that scientists and fuel cell developers in general, are using in order to have better and cheaper catalysts. Many have made a great impact on CL structures. Some approaches included supporting material but others considered unsupported catalysts too. The aspect ratio of particles has been recognized as a relevant factor. Metallic membranes, meshes, and bulk materials have also been considered of which the structural features will impact on the final structure and functionality of fuel cell technology. Local structures and at different levels of scale are still subjects of interest in many scientific works (Soboleva et al, 2010). 

Polymer Membranes in Fuel Cells takes an in-depth look at the new chemistries and membrane technologies that have been developed over the years to address the concerns associated with the materials currently in use. Unlike the PFSAs, which were originally developed for the chlor-alkali industty, the more recent hydrocarbon and composite materials have been developed to meet the specific requirements of PEM Fuel Cells. Having said this, most of the work has been based on derivatives of known polymers, such as poly(ether-ether ketones), to ensure that the critical requirement of low cost is met. More aggressive operational requirements have also spurred the development on new materials for example, the need for operation at higher temperature under low relative humidity has spawned the creation of a plethora of new polymers with potential application in PEM Euel Cells. 

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