hydrogen production from water using solar cells powered nafion ...

• Good film-formation
• High proton conductivity (especially at low relative humidity)
• Low electronic conductivity
• Water retention above 100 o C
• Thermal, oxidative and hydrolytic stability
• Effective reactant separator
• Capable of fabrication into MEA’s
• Mechanical durability at high temperature (80 – 140 o C) for long times
Formerly, DuPont (Nafion®), Dow, and Asahi (Aciplex® and Flemion®)
perfluorosulfonic acid polymers have been considered as an unique and nearly optimal
materials to serve as separators in both electrolyzers and PEM fuel cells. However, they
cannot meet the most important requirement: The cost of a PEM (e.g. 600- 700 $/m 2 ).
Recently, some of the most promising candidates for proton exchange membranes have
been reported as polyamides, poly(ether ketone)s, poly(arylene ether sulfone)s and
polybenzimidazoles (Rikukawa and Sanui 2000). The advantages of using these new
candidate materials are their lower cost as compared to well-known perfluorinated
membranes, such as Nafion, the inclusion of polar groups to improve water uptake over a
range of temperatures, and also the possibility of recycling of these new candidates by the
conventional methods (Rikukawa and Sanui 2000). Although there are no commercial
supply of these new types of PEM’s in the market, there is a great effort to commercialize
them, such as by Dais-Analytic Co. and Odessa Co. Also, the pioneering fuel cell maker,
Ballard Co., is working with the Victrex USA Co. and Greenville Co. to produce
alternative new membrane based on sulphonated polyaryletherketone resin supplied
(WEB_3 2006). Nafion ® is currently almost an industry standard with its various types. It
is fabricated from a copolymer of tetrafluoroethylene (Teflon ® ) and perfluorinated
monomers contain sulfonic acid groups. The general formulation of the Nafion ® is given in
Figure 2.3 below.
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