The coaxial nanofiber microstructure facilitates continuous conduction and reinforce in proton exchange membranes with reduced Nafion content

Proton exchange membranes with high proton conductivity, reducing swelling and cost are the research focusses in their application for fuel cells. In this study, the unique coaxial nanofiber microstructure divides shell and core functional layers for the conductive Nafion and reinforcing poly(vinylidene fluoride) (PVDF) components, respectively to optimize conduction-reinforce properties of the membrane. The PVDF fiber-forming core drags Nafion to form the shell layer, addressing the spinnable limitations of Nafion perfluorosulfonic acid polymer. Up to 100 wt% of Nafion microphase in the shell layer enhances continuity of proton conducting channels, and up to 100 wt% PVDF microphase in the core layer reinforces the membrane. PVDF core layer endows coaxial nanofiber membrane with extremely low swelling ratio of 1.5 % at 80 °C. The coaxial nanofiber microstructure ensures 100 % Nafion continuity in the shell layer, reducing overall Nafion content to 77.5 wt % but increasing proton conductivity to 241.9 mS cm⁻¹ and fuel cell peak power density of 1119.3 mW/cm² at 80 °C, 19.6 % and 27 % improvements, respectively over Nafion 211. The coaxial functional zoning design-offers an optimized microstructure for high-performance proton exchange membranes.