Conductivity of composite membrane-based poly(ether-ether-ketone) sulfonated (SPEEK) nanofiber mats of varying thickness

Abstract

Nanofiber mats of SPEEK_70wt%–PVB_{30 wt%} (polyvinyl butyral)-based composite membranes were prepared by varying the electrospinning time in order to obtain mats with different thicknesses. These mats were embedded in SPEEK_65wt%–PVA_35wt% (polyvinyl alcohol) polymer solution to fill the pores in the fibers. The obtained membranes with different mat thicknesses have been characterized by water uptake, ionic exchange capacity, scanning electron microscopy, mechanical properties and proton conductivity. Microtensile test studies reveal that the maximum tensile strength increases as the thickness of the SPEEK–PVB nanofiber mats increases, resulting in more flexible composite membranes compared to a pure SPEEK–PVA membrane obtained by casting. The proton conductivity occurs more easily through the nanofiber than through the matrix phase, and the best conductivity (0.038 S cm⁻¹) was measured at 120 °C for the composite membrane of SPEEK–PVB nanofiber mats obtained after 12 hours of electrospinning time. This value suggests that our composite membranes have high potential to function in the temperature range between 100 and 140 °C without losing their strength and while maintaining their high proton conductivity, making them an excellent candidate for fuel cells that operate at intermediate temperatures.