Improved performance of nafion membranes by blending ultra-high molecular weight polyvinylidene fluoride

Abstract

Proton exchange membrane (PEM) is developing towards thin thickness and high mechanical strength for extraordinary performance proton exchange membrane fuel cells (PEMFCs). However, the commercial membrane such as Nafion can hardly satisfy the practical application of PEMFCs because of high gas crossover and low mechanical strength when the thickness is less than 20 μm. Here, a reinforced composite membrane (denoted as P110-PFSA) was synthesized by blending poly(vinylidene fluoride)(PVDF) featured with high molecular weight of Mw= 1100000 g mol-1 into perfluorosulfonic acid resin (PFSA). The P110-PFSA with the thickness of 15 μm exhibits tensile strength of over 33 MPa because the PVDF with high molecular weight forms a higher density of hydrogen bonds with PFSA, resulting in a reinforcement of the bonding strength between PVDF and PFSA. H2/O2 fuel cell performance with the P110-PFSA shows more than 1170 mW cm-2 fed with H2 at 70 °C and 100% RH much better than that with Nafion 211. Direct methanol fuel cell power densities of the blent PEM are 92, 61, 50, 28 and 15 mW cm-2 fed with 2, 6, 10,16 and 20 M methanol solution respectively at the anode.