High level of solid superacid coated poly(vinylidene fluoride) electrospun nanofiber composite polymer electrolyte membranes

Electrospun fiber-based composite polymer electrolyte membranes (PEMs) with artifically constructed longrange proton conductive channels have been drawn considerable attention due to their promising applications in fuel cells. Herein, high level of superacidic phosphotungstic acid (PWA) coated poly(vinylidene fluoride) (PVDF/ PWA) electrospun mat as a new three-dimensional proton conducting network was prepared using a polydopamine-assisted coating method. Polydopamine can homogeneously adhere PWA on the PVDF nanofibers' surface. This new mat was then used to fabricate PEMs after filled with polycation chitosan. With the introduction of the PVDF/PWA network, the obtained chitosan filled composite membrane showed significantly improved proton conductivity, which was about one order of magnitude higher than that of the chitosan filled pure PVDF membrane. Moreover, the chitosan can not only effectively inhibit the leaching out of PWA through the strong static interaction between chitosan and PWA, but also act as an ionomer matrix to further increase the proton transport. The direct methanol fuel cell of the PVDF/PWA composite membrane exhibits a peak power density of 85.0 mW cm(-2), whereas it is only 47.5 mW cm-2 for the membrane without PWA coating. Consequently, this study provides a new strategy to design high-performance PEMs by utilization of solid superacid coated electrospun nanofibers.