Enhancement of proton/methanol selectivity via the in-situ cross-linking of sulfonated poly (p-phenylene-co-aryl ether ketone) and graphene oxide (GO) nanosheets

Abstract

It has been reported that introducing graphene oxide (GO) or functionalized GO into proton exchange membranes (PEMs) can inhibit methanol diffusion by increasing the complexity of the methanol diffusion pathway in the hydrophilic region. In fact, methanol permeation also occurs in the hydrophobic area, which is very important, but rarely studied. In this study, we propose a facile and effective in-situ cross-linking method to prepare GO/sulfonated poly (p-phenylene-co-aryl ether ketone) crosslinked PEMs. By using the sulfonic acid group in parent polymer as a solid acid catalyst, the –COOH groups in GO undergo the Friedel-Craft acylation with the nucleophilic phenyl rings in the hydrophobic segments under vacuum heating, and the construction of covalent cross-linking network between GO and hydrophobic region is achieved successfully. The obtained crosslinked membranes show obviously reduced methanol crossover and greatly enhanced selectivity. The highest power density of the passive DMFC is obtained by using the 2 wt% GO crosslinked membrane and its value (28.1 mW cm-2) is higher than the original parent polymer (24.4 mW cm-2). These results demonstrate that the hydrophobic phase is closely relevant to the transport of methanol molecules in the membrane, which provides a new idea for the construction of methanol-blocking PEMs.