Azide-assisted crosslinked quaternized polysulfone with reduced graphene oxide for highly stable anion exchange membranes

As an important component for anion exchange membrane fuel cells (AEMFCs), anion exchange membranes (AEMs) should possess good mechanical strength and relatively high stability in alkaline environment. Besides, fuel permeation as a serious issue which may lead to the potential decrease and catalyst poisoning could also affect the application for AEMs. Herein, we prepared a series of crosslinked composite membranes which using reduced graphene (rGO) as both inorganic nanofillers and crosslinkers. During a simple thermal crosslinking at 160 °C, a covalently cross-linked structure was formed between side chains with azide groups and rGO with alkenyl groups without sacrificing ionic groups. Properties such as water uptake (WU) and swelling ratio were significantly decreased after crosslinking, which caused the decline of ion conductivity for the membranes. However, it was found that when only a small amount of rGO (less than 0.5 wt%) was incorporated into QPSU to induced crosslinking, the methanol permeability of membranes obviously decreased by two orders of magnitude, and the mechanical strength and thermal stability of the composite membranes were enhanced. Moreover, the crosslinked membrane maintained stable in Fenton's reagent and exhibited high alkaline resistance in 1 M of KOH at 60 °C for more than 500 h. Therefore, the crosslinked membranes with rGO demonstrate great potential as anion exchange membrane for fuel cell.