Enhanced mechanical durability of perfluorosulfonic acid proton-exchange membrane based on a double-layer ePTFE reinforcement strategy

Although widely used as proton-exchange membranes (PEMs), perfluorosulfonic acid (PFSA) membranes suffer from critical mechanical degradation under alternating wet/dry conditions. A common method for improving the mechanical durability of PFSA mem-branes is to intercalate single-layer expanded polytetrafluoroethylene (ePTFE). As rein-forcement skeletons, the different numbers of ePTFE layers can be expected to have different effects on the mechanical durability of PFSA-based PEMs. In this study, double layers of ePTFE reinforcement are intercalated into PFSA ionomer to further enhance the mechanical durability of such membranes. The mechanical strength in directions A and B of the double-layer ePTFE reinforced membrane (DR-M) are 36.52 and 37.12 MPa, which are significantly higher than those (24.37 and 27.51 MPa) of the single-layer ePTFE reinforced membrane (SR-M). The area swelling rate of the DR-M is 11.91%, which is lower than that (15.53%) of SR-M. It is precisely due to the additional rigid ePTFE skeleton for the DR-M that the yield strength and modulus of the PFSA membrane are further improved, resulting in the higher resistance to plastic deformation. After 3000 cycles of alternating wet/dry conditions, DR-Ms exhibited no significant hydrogen crossover current increase (from 3.01 mA cm-2 to 2.98 mA cm-2), reduced H2/Air fuel cell performance attenuation (by 4.9%), smaller membrane impedance increase (by 6.2%), and reduced membrane structure failure (less cracks) compared with SR-Ms. In short, the described double-layer ePTFE enhance-ment strategy provided a fresh perspective for improving the mechanical durability of PEMs.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

In this study, double layers of ePTFE reinforcement were intercalated into PFSA ionomer to improve the mechanical durability of PEMs. The double-layer ePTFE reinforcement significantly increased the mechanical strength and reduced the area swelling rate. Additionally, the double-layer ePTFE enhanced membranes showed better performance and durability under alternating wet/dry conditions compared to single-layer ePTFE reinforced membranes.