Reinforced Composite Membranes Based on Expanded Polytetrafluoroethylene Skeletons Modified by a Surface Sol–Gel Process for Fuel Cell Applications
Lei Liu, Yizhe Li, Rui Qiao, Yijing Xing, Haibin Li
Abstract
Intercalating expanded polytetrafluoroethylene (ePTFE) reinforcements and incorporating antioxidants (e.g., CeO2 and ZrO2) into perfluorosulfonic acid (PFSA) ionomers are typical methods used to improve the physical and chemical durability of PFSA-based proton exchange membranes, respectively. Nevertheless, these two popular methods still suffer from respective inherent limitations, including the poor interfacial binding between hydrophobic ePTFE and polar PFSA ionomers and the migration and loss of incorporated antioxidants. To solve these two issues simultaneously, we propose a solution based on a surface sol–gel process, by which the deposition of ZrO2 coating on polydopamine-modified ePTFE skeletons not only improves the interfacial bonding of the skeletons and PFSA ionomer but also restrains the migration and loss of antioxidant additives. The results show that the ZrO2-deposited ePTFE exhibits improved hydrophilicity and the reinforced composite membranes based on the modified ePTFE skeletons with one layer of ZrO2 coating are endowed with superior proton conductivity, mechanical properties, dimensional stability, and open-circuit voltage durability. In addition, the stability of the ZrO2 coating on the ePTFE skeletons is also verified.