Advances in Hybrid Organic-Inorganic Proton Exchange Polymer Membranes Incorporating Heteropoly Acids

We describe a new class of materials for proton conduction for proton exchange membrane (PEM) fuel cell applications based on the heteropoly acids (HPAs). HPAs are readily functionalized by a variety of moieties including polymerizable organic groups. These hybrid monomers are polymerized into polypolyoxometallates (polyPOMs). The materials are characterized by IR, NMR, and SAXS. Proton diffusion coefficients are measured by Pulse Field Gradient Spin Echo NMR and are observed to increase with temperature. In-plane proton conductivity measurements show that performance similar to a state-of-the-art PFSA ionomer is obtained at 80 °C and 100 % RH. Conductivities at lower RH or higher temperature are not yet sufficiently high. For these first generation materials many problems still need to be addressed in order to fabricate materials with all the required properties for a next generation PEM