Facile enhancement in proton conductivity of sulfonated poly (ether ether ketone) using functionalized graphene oxide—synthesis, characterization, and application towards proton exchange membrane fuel cells

A SO₃H-functionalized graphene oxide-incorporated sulfonated poly (ether ether ketone) (S-GO/SPEEK) composite membrane was fabricated via the solution casting method, and the performance of the prepared membrane toward proton exchange membrane fuel cell (PEMFC) electricity generation was evaluated. Infrared spectroscopic measurements revealed the presence of sulfonic acid, hydroxyl and carboxyl functional groups in the composite membrane. The distribution of sulfonated graphene oxide (S-GO) throughout the SPEEK matrix has been examined using FE-SEM and found to be uniform. The ionic conductivity and thermal stability of the SPEEK have been greatly increased with the incorporation of the S-GO fillers, owing to the generation of extended proton conducting highways and strong interfacial interactions. S-GO effectively binds with ring structures and SO₃H groups of SPEEK through П–П stacking and hydrogen bonding, respectively, which leads to good mechanical integrity and prevents the swelling of the membranes even in an aqueous environment. Besides, SO₃H groups in S-GO assist to increase the functional group intensity in the composite, leading to extended water retention and proton conducting properties. The S-GO/SPEEK membrane exhibited a maximum power density of 0.485 W m⁻², which is 1.08 and 1.17-fold higher than that of GO/SPEEK (0.445 W m⁻²) and SPEEK (0.414 W m⁻²), respectively.