Radiation grafted ETFE-graft-poly(α-methylstyrenesulfonic acid-co-methacrylonitrile) membranes for fuel cell applications

A new membrane material for polymer electrolyte fuel cells (PEFC), ETFE-graft-poly(α-methylstyrenesulfonic acid-co-methacrylonitrile), is presented. Its preparation by radiation-induced grafting and the dependence of the reaction kinetics on the irradiation dose (3 and 15 kGy) and crosslinker concentration are reported. A series of divinylbenzene crosslinked and uncrosslinked membranes is characterised with respect to ion exchange capacity (IEC) (up to 2.1 mmol/g), proton conductivity (up to 92 mS/cm at room temperature), and water uptake (10–67%). Furthermore, the correlation between the dimensional stability of the membrane and the graft level is presented. The ex situ hydrolytic stability of the membranes was tested and analysed by infrared (IR) spectroscopy. In a hydrogen/oxygen PEFC at 80 °C, Nafion 212 and a 35 μm thick grafted membrane showed the same performance, whereas the hydrogen permeability of the grafted membrane is only one third compared to that of Nafion 212.