Regulation of the Properties of Nafion and PVDF Nanofibrous Membranes by Designing Fiber Structures

Nafion and polyvinylidene fluoride (PVDF) nanofibrous membranes have received more attention due to their high performances as proton exchange membranes, catalyst supports, and binders in fuel cells. In this paper, regulations of the properties of Nafion and PVDF nanofibrous membranes by designing fiber structures are investigated. Three Nafion and PVDF nanofibrous membranes with an ~50% PVDF content, the blended Nafion/PVDF (N/P) and two core-shell PVDF-Nafion and PVDF-N/P with PVDF as the core, and Nafion, a mixture of Nafion and PVDF respectively as the shell, are fabricated by single-needle or coaxial electrospinning, then hot-pressed, annealed, and acidized. XRD spectrums manifest that PVDF and Nafion mutually promote the crystallization, and annealing further improves the crystallinity. Compared with Nafion 117 membranes, three nanofibrous membranes show greater mechanical properties and lower water uptake, swelling, and conductivity. PVDF-Nafion and PVDF-N/P reveal greater stress and conductivity than N/P. PVDF-Nafion and PVDF-N/P increase the broken stress to about 50 MPa, almost five times Nafion and three times N/P. PVDF-Nafion shows the highest conductivity of 0.0493 S/cm, 27% lower than Nafion, exhibiting a potential application prospect. The experimental results are significant for cost-effectively optimizing the performances of Nafion and PVDF nanofibrous membranes on a large scale.