Aligned electrospun nanofibers as proton conductive channels through thickness of sulfonated poly (phthalazinone ether sulfone ketone) proton exchange membranes

Abstract

Abstract A novel approach is proposed to fabricate sulfonated poly (phthalazinone ether sulfone ketone) (SPPESK) proton exchange membranes with ordered through-plane electrospinning nanofibers, which provide nano-scale through-plane proton conductive channels along the thickness direction of the membranes, aiming to satisfy the challenging requirement of high through-plane proton conductivity in fuel cell operations. Induced by electrostatic attraction of strong electric field, the negatively charged sulfonic acid groups tend to aggregate towards surface of the electrospun fibers, which is evidenced by TEM and SAXS and further induces aggregation of the sulfonic acid groups in the SPPESK inferfiber voids filler along the surface of the nanofibers. The aligned electrospun nanofibers carries long-range ionic clusters along the thickness direction of the membrane and results in much higher total through-plane conductivity in the thickness aligned electrospun membranes, nearly twice as much as that of the cast SPPESK membrane. With smooth treatment, the thickness aligned electrospun SPPESK membranes exhibit higher single cell power density and tensile strength as compared with Nafion 115 (around 1.2 and 1.5 folds, respectively). Such a design of thickness aligned nano-size proton conductive channels provide feasibility for high performance non-fluorinated PEMs in fuel cell applications.