Improved electrochemical performance of composite anion exchange membranes for fuel cells through cross linking of the polymer chain with functionalized graphene oxide

Novel anion conductive nanocomposite membranes with superb hydroxide conductivity and chemical durability in alkaline conditions were prepared by the introduction of quaternary ammonium functionalized graphene oxide (Q-GO) into quaternized poly(arylene ether) (QPAE) random copolymer. Q-GO containing amino silane units, which induce ion cluster formation in the polymer matrix, was synthesized using (3-aminopropyl)triethoxysilane (APTS) and (3-bromopropyl)trimethyl ammonium bromide (PTMA) as the main quaternization reagents. The chemical structures and morphologies of the polymers and inorganic nanofillers were characterized by ¹H NMR, FT-IR, FE-SEM, XPS, and SAXS. GO-(APTS-c-PTMA), the so called Q-GO, was used to expand the ion transfer sites and improve the physicochemical stability of the membrane. The electrochemical properties, thermal/mechanical properties, and chemical stabilities of the anion exchange membranes (AEMs) were investigated in accordance with different contents of GO-(APTS-c-PTMA). The π-π bonds between the polymer matrix and the Q-GO resulted in improved dimensional stability and mechanical properties in the composite membrane. The QPAE/GO-(APTS-c-PTMA) 0.7 wt% membrane showed the highest hydroxide conductivity of 114.2 mS cm⁻¹ at 90 °C with an ion exchange capacity of 1.45 mmol g⁻¹, which is 2.07 times higher than the pristine membrane (55.1 mS cm⁻¹ at 90 °C). Furthermore, the single-cell performance of the QPAE/GO-(APTS-c-PTMA) 0.7 wt% as an AEM showed an excellent maximum power density of 135.8 mW cm⁻² at 70 °C.