Perfluorosulfonic acid membranes modification

Fig. 3 shows temperature dependences of conductivities in vacuum before and after heating the perfluorosulfonic acid membrane at the dose of 14 kGy to 393 K. The conductivities after heating decreased at higher temperature and reached to that for the unirradiated one at lower one. Particularly, it was found that the new protonic conduction process at lower temperature disappeared by heating. Moreover, it was confirmed that the conductivity increased again when was exposure to air at room temperature for 20 days. The conductivity depends on humidity in the enviroiunents and, namely, contents of water and hydrogen in the membrane. The modification for the absorption characteristic of water on the topmost surface greatly contributes to the new conduction mechanism at lower temperature. 

Moon GY, Rhim JW (2008) Self-assembly modification of perfluorosulfonic acid membranes for the application to direct meytahnol fuel cells. Macromol Res 16 524—531... 

Lue, S.J., Hsiaw, S.-Y. and Wei, T.-C. 2007. Surface modification of perfluorosulfonic acid membranes with perfluoroheptane (C7F16)/argon plasma. 

Subianto, S., Pica, M., Casciola, M., Cojocaru, P, Merlo, L., Hards, G., Jones, D. J., Physical and chemical modification rentes leading to improved mechanical properties of perfluorosulfonic acid membranes for PEM fuel cells. J. Power Sources 2013, 233 (0), 216-230. 

Abstract There have been numerous studies on modifying DuPont s Nafion (a perfluorosulfonic acid polymer) in order to improve the performance of this membrane material in a direct methanol fuel cell. Modifications focused on making Nafion a better methanol barrier, without sacrificing proton conductivity, so that methanol crossover during fuel cell operation is minimized. In this chapter, a brief literature survey of such modifications is presented, along with recent experimental results (membrane properties and fuel cell performance curves) for (1) thick Nafion films, (2) Nafion blended with Teflon-FEP or Teflon-PFA, and (3) Nafion doped with polybenzimidazole. 

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