Acidic and Basic Polymer-Grafted Graphene Oxides as Functional Fillers for High-Performance Hydrocarbon-Based PEMs

Abstract

Sulfonated poly(arylene ether sulfone) (SPAES)-based composite membranes incorporating functionalized graphene oxides (GOs) were systematically developed to investigate the effect of acidic and basic GO fillers on the enhancement of proton exchange membrane (PEM) performance for fuel cell applications. Two types of GO fillers, sulfonated polysulfone (SPSf)-grafted GO (SPSf-GO) and triazolated polysulfone (TPSf)-grafted GO, were synthesized and embedded into the SPAES matrix. The incorporation of these functionalized GOs promoted the formation of well-connected ionic transport networks, resulting in increased water uptake (WU) and improved proton conductivity. Among the developed membranes, the SPAES/TPSf-grafted GO (TPSf-GO) composite membrane exhibited superior mechanical toughness, dimensional stability, and oxidative durability while maintaining high proton conductivity, particularly under low-humidity conditions. These improvements were attributed to strong acid-base interactions between the triazole groups in TPSf-GO and the sulfonic acid groups in SPAES, thereby reinforcing the polymer network and facilitating additional proton conduction pathways. The membrane electrode assembly (MEA) with SPAES/TPSf-GO exhibited cell performance comparable to that of a commercially available perfluorosulfonic acid (PFSA) membrane. These findings suggest that basic-functionalized GO can serve as a promising filler for next-generation PEMs, providing a scalable and effective strategy to simultaneously improve proton transport and membrane durability.