(Invited) Development of PFSA Ionomers for the Membrane and the Electrodes

Asahi Glass Company (AGC) has been developing the PFSA ionomers for the membrane and electrodes. Ionomers for the membrane are required to have high ion exchange capacity (IEC) but the water uptake should be below certain level to avoid excess dimensional changes during dry and wet operating condition cycles. Polymer electrolytes with high softening temperatures and high proton conductivity were prepared and tested in various conditions. For the cathode electrode, polymer electrolytes with high oxygen permeability were prepared with the assumption that the flux of oxygen can be the rate limiting step for the reaction. Oxygen permeability of polymer electrolytes was increased by decreasing their density. The performances of MEAs using high oxygen permeable ionomers in the cathode were tested and they showed improved performances compared to the MEA using conventional ionomers especially when the Pt loading was low. The ionomer was also used in the micro porous layers (MPLs) between the catalyst layers and the Gas diffusion substrate to create hydrophilic MPLs. The MEAs applying them were explored to achieve better performances at dry conditions as well as at wet conditions.