Application of spirobiindane-based microporous poly(ether sulfone)s as polymeric binder on solid alkaline exchange membrane fuel cells

In this report, we introduced spirobiindane group to poly(arylene ether sulfone) (PES) to build the structure of polymers with intrinsic microporosity (PIMs). A novel PESs (QOH-SBIs), which have spirobiindane and tetra (quaternary ammonium) hydroxide pendant moieties, were synthesized for anion-conducting binder material in membrane electrode assembly (MEA) of solid alkaline exchange membrane fuel cell (SAEMFC). The time-lag method was used to check the high gas permeability of the polymers. The high permeability is due to the micro-pores at the molecular level that is formed by the difference in chain thicknesses between two alternating units, thick spirobiindane group and thin arylene ether sulfone group. QOH-SBIs shows a semi-rigid chain conformation in a solution. The inter-chain spacing and chain conformation were measured with wide angle X-ray diffraction (WAXD) and small angle neutron scattering (SANS), respectively. High gas permeability directly affected the performance of SAEMFC. The MEA with spirobiindane-modified PES shows much higher maximum power density than that of spirobiindane-free PESs.