Enhancement of sulfonated poly(ether ether ketone)-based proton exchange membranes doped with different ionic liquids cations

Abstract

Herein, to balance the overall performance of SPEEK membrane, the imidazolium hydrogen sulfate (Im.HSO4), 1-methylimidazolium hydrogen sulfate (MI.HSO4), and 1-butyl-3-methylimidazolium hydrogen sulfate (BMI.HSO4) ionic liquids (ILs) were used as dopants in polymer matrix. A series of SPEEK/ionic liquid composite membranes were successfully fabricated by casting method and evaluated. Comparative studies showed that the membranes doped with 5 wt.% of MI.HSO4 or BMI.HSO4 ILs showed an increase in the proton conductivity of 50% and 30% at 80 °C, respectively, compared with the pristine SPEEK membrane. The proton exchange membrane fuel cell (PEMFC) performance demonstrated that the membrane doped with 5 wt.% of BMI.HSO4 IL (SBMI5) has the highest current density value and the highest power density without loss of performance as temperature increases. This result indicates that this membrane is promising for fuel cells application.