Facile and affordable synthesis of sulfonated and phosphonated poly (p-terphenyl perfluorophenyl)s for proton exchange membrane fuel cells

Abstract

Hydrocarbon proton exchange membranes (PEMs) which exhibit low-cost, improved robustness, and simple synthesis relative to perfluorosulfonic acid (PFSA) membranes, are of great significance for proton exchange membrane fuel cells (PEMFCs). Herein, we report a facile and affordable preparation of sulfonated and phosphonated poly (p-terphenyl perfluorophenyl)s PEMs via superacid-catalyzed Friedel−Crafts condensation of p-terphenyl and pentafluorobenzaldehyde monomers, following by highly selective para-substitution of fluorobenzene to graft ion exchange groups. The rigid and well-defined polymer structure with precisely controlled anionic groups, enables good phase separation and efficient ionic clustering to promote proton transport. Sulfonated and phosphonated PEMs show modest proton conductivities of 150 and 120 mS cm⁻¹ at 90 °C, and achieve H₂/air PEMFC peak power densities of 360 and 237 mW cm⁻² at 80 ℃, respectively. Interestingly, we find that phosphonated PEMs have significantly higher resistance to free radicals than sulfonated PEMs. Overall, the results suggest that our prepared hydrocarbon PEMs have potential applications for fuel cells.