Enhancing Proton Conductivity of Sulfonated Poly(ether ether ketone)-Based Membranes by Incorporating Phosphotungstic-Acid-Coupled Graphene Oxide

Constructing long-range proton-transfer pathways with sufficient conducting sites in proton exchange membranes (PEMs) is vital for proton conduction. Herein, phosphotungstic-acid-coupled graphene oxide (HPW@mGO) is prepared by grafting imidazolium ionic liquids (IMILs) on GO nanosheets, followed by loading with HPW via the electrostatic interaction. HPW@mGO nanosheets are then integrated into polymers to prepare sulfonated aromatic poly(ether ether ketone) (SPEEK)/HPW@mGO nanohybrid membranes. The proton conductivities of the nanohybrid membranes under various humidity conditions are enhanced significantly due to the distinct proton conduction behavior of HPW and IMILs as well as the long-range two-dimensional (2D) interfacial ionic pathways. Specifically, the SPEEK/HPW@mGO-4 membrane achieves a maximum proton conductivity of 5.0 × 10–3 S cm–1 at 65 °C and 40% RH, about 32.3 times that of the pristine SPEEK membrane. Meanwhile, the SPEEK/HPW@mGO-4 membrane shows a 108% increment of the maximum power density. The results demonstrate that 2D materials with long-range ionic pathways are promising fillers for proton transfer.