Incorporating imidazolium-functionalized graphene oxide into imidazolium-functionalized poly(ether ether ketone) for enhanced hydroxide conductivity

The enhancement of hydroxide conductivity in anion exchange membrane fuel cells is of great urgency. Incorporation of fillers with abundant ion exchange groups into polymer electrolyte offers availability to robust membranes with improved ion conductivity. In this study, imidazolium-functionalized graphene oxide (ImGO) was prepared by polydopamine coating on the pristine graphene oxide sheets and subsequent reaction with imidazolium. Then, the ImGO was incorporated into imidazolium-functionalized poly(ether ether ketone) (ImPEEK) matrix to fabricate ImPEEK/ImGO hybrid membranes. Benefiting from the abundant imidazolium groups on ImPEEK and ImGO, the ImPEEK/ImGO hybrid membrane possesses a high ion exchange capacity up to 2.59 mmol g−1 with a moderate water uptake and good mechanical strength simultaneously. The interconnected hydrogen-bonded networks formed between the functional groups and the absorbed water contribute to the maximum hydroxide conductivity of 0.14 S cm−1 at 70 °C and 100% RH at the ImGO loading content of 4 wt%. The ImPEEK/ImGO-4 hybrid membrane shows an improved fuel cell performance with the power density of 50.04 mW cm−2 at 50 °C which is 122% higher than that of the pristine ImPEEK membrane. Moreover, the alkaline and thermal stability of the hybrid membranes are also enhanced.