A Study On Proton Exchange Membranes For Direct Methanol Fuel Cell Applications

Direct methanol fuel cells (DMFC) have attracted considerable attention as an alternative to the present power sources, since they offer numerous benefits, including high efficiency, high power density, low or zero emissions and easy fuel carriage. DMFC are expected to find wide application as a portable or mobile power, exemplified by battery for cellular phones or engine for electric vehicles. However, at present, two major technology problems in DMFC still restrict their performances and applications. One problem is the crossover of methanol through the proton exchange membranes. The other is slow methanol oxidation kinetics on the anode catalyst. In this study, development of methanol barrier conducting membranes was attempted.Sulfonated polyether ether ketone (SPEEK) is a very hopeful alternative membrane material for direct methanol fuel cells. However, with fairly high degree of sulfonation (DS) and when approaching high temperature, SPEEK membranes can heavily swell or even dissolve. This restricts the membranes from working above a high tolerable temperature, which otherwise enables high proton conductivity. To deal with this contradictory, polyaniline (PANI) was employed to blend with SPEEK, with the attempt to take advantage of the interaction between acid and base groups of the two polymers. Results show that not only the temperature tolerance but also the methanol resistance of the SPEEK-blend-PAN membranes is greatly improved. High proton conductivity of the blend membranes can be also achieved because of increased high tolerable temperature.