Towards performance improved anion exchange membrane: Cross-linking with multi-cations oligomer modified graphene oxide

Cross-linking structure has been proven to be an effective approach to address the balance issue between ionic conductivity, dimensional stability and other properties of anion exchange membranes (AEMs). Here, a novel multi-cationic oligomer was synthesized from 1,4-diazabicyclo [2,2,2]octane and 1,6-dibromohexane, and subsequently used to prepare multi-cationic oligomer brushes-decorated graphene oxide (QBGO). The obtained QBGO was employed as the cross-linker to form cross-linked poly (arylene ether sulfone) (QPAES) AEMs by end-cap tertiary amine coupling reaction. Benefiting from the introduction of the multi-cations and flexible long-chain cross-linker structure, the cross-linked QPAES/QBGO membranes formed hydrophilic/hydrophobic phase-separation microstructures and well-defined ionic channels which are responsible for water uptake and ion transfer. As a result, the cross-linked QPAES/QBGO-2.0 membrane exhibited 1.90-fold higher ionic conductivity and better chemical stability than the control QPAES membrane. The QPAES/QBGO-2.0 membrane displayed a higher power density of 75.7 mW cm−2 than that of the control QPAES membrane (53.1 mW cm−2) in a H2/O2 fuel cell test. In a word, we propose that this novel design strategy holds broad prospects for the design of new polymer electrolyte membrane materials.