Sulfonated pentablock terpolymers as membranes and ionomers in hydrogen fuel cells

Abstract In this study, a series of sulfonated hydrocarbon pentablock terpolymers (NEXAR® Polymers) with different ion exchange capacities (1.0, 1.5, and 2.0 meq g−1) were characterized and investigated as membranes and ionomers in hydrogen fuel cells. All NEXAR® Membranes exhibited higher proton conductivity (>0.2 S cm−1 at 80 °C, 90% RH) than Nafion (the most frequently used polymer membrane in hydrogen fuel cells). The NEXAR® Membrane (with Nafion ionomer) also exhibited higher fuel cell performance than Nafion at 50 °C, 100% RH. At higher fuel cell operating temperatures (80 °C, 100% RH), the fuel cell performance of the NEXAR® Membranes were lower than Nafion and performance of the lower ion exchange capacity NEXAR® Membrane (1.0 meq g−1) was more stable than the higher ion exchange capacity NEXAR® Membranes (1.5 and 2.0 meq g−1). Differences in membrane cell resistances and more significant differences in proton conductivity before and after fuel cell conditions between NEXAR® Membranes and Nafion membranes corroborates with fuel cell performance results. Optimization (catalyst ink composition, i.e., solids and solvent ratio) and fuel cell performance of membrane electrode assemblies with NEXAR® Polymer as both the membrane and the ionomer were also investigated. These results show promise for NEXAR® Polymer as a commercially viable low-cost alternative proton exchange membrane and ionomer for hydrogen fuel cells.