Synthesis study of fluor-free membranes for DMFC applications

Direct methanol fuel cells (DMFC) were developed for a variety of applications and different markets. Such applications range from micro fuel cells as a battery replacement in small electronic devices such as mobile phones or laptops. Thus, primary advantages of DMFCs over existing battery technology are increased power density and energy storage capacity as well as the potential for uninterrupted operations. A number of per-fluorinated proton conducting polymeric membranes was created for fuel cell application. However, until now the main problems of their applications remain elevated cost of production and high methanol crossover [1,2]. In this work is presented a new family of membranes for DMFC application based on cheap fluorine free chemistry with possibility of the membrane properties tuning in high range. This approach is based on the treatment of industrial polyolefln films with gamma-irradiation, then a radical polymerization of vinyl aromatic monomers leading to the formation of interpenetrated polymers with aliphatic backbone and aromatic side chains (i.e grafting process). Following sulfonation of these polymers into aromatic rings leads to the formation of fluorine free membranes for DMFC application. Several parameters like grafting and sulfonation time as well as temperature are studied for obtaining suitable electrochemical and physico-chemical properties for low temperature (i.e. 40degC) DMFC applications. Are presented Proton Conductivity, Ionic-Exchange Capacity (IEC), Water Up-Take, MeOH Permeability, SEM cross-section and FTIR analysis. All those data verify the tunability of the properties for such kind of protonic membrane in function of the final specifications.