Novel nanofiber-enhanced SPEEK proton-exchange membranes with high conductivity and stability

In this article, a novel proton exchange membrane, shown both high proton conductivity and excellent stability, has been demonstrated, which is simply fabricated by embedding poly(vinylidene fluoride) grafted poly(styrene sulfonic acid) (PSSA-g-PVDF) nanofibers in sulfonated poly (ether ether ketone) (SPEEK) matrix. The novel nanofiber-enhanced membrane (NEM) presents an utlra-high proton conductivity of 720.6 mS/cm, which is 2.4 times higher than the unmodified SPEEK membrane. The long-range continuous proton transport channel built at the interface between the matrix and nanofibers, known as acid-condensed layer, has been directly confirmed by transmission electron microscopy (TEM) measurements for the first time, which illustrates the result. Futher-more, the NEMs are always provided with the excellent dimensional, thermal, and mechanical stability, which benefit from the sturdy three-dimensional network of PSSA-g-PVDF nanofibers. In virtue of the high conductivity and stability, the NEMs have proved to be very promising in fuel cells.