Nanohybrid membranes with hydroxide ion transport highways constructed from imidazolium-functionalized graphene oxide

Graphene oxide (GO) and functionalized GO have been widely employed to design and fabricate polymer-inorganic nanohybrid materials for electrochemical applications. In this study, a series of imidazolium-functionalized graphene oxide (ImGO) nanosheets bearing different types of ligands (namely butyl, decyl, carbethoxy, and benzyl groups) on quaternary ammonium (QA) groups are prepared via distillation-precipitation polymerization and quaternarization, and then embedded into chitosan (CS) to fabricate nanohybrid membranes. The addition of ImGO significantly enhanced the thermal, mechanical, and anti-swelling stabilities of membranes due to the strong electrostatic attractions at CS/ImGO interface. More importantly, hydroxide ion transport highways were constructed at CS/ImGO interface via interfacial interactions. Meanwhile, the influence of the ligands on QA groups on the physicochemical properties, OH- conductivity, and conduction mechanism is systematically elucidated. Due to the optimal hydrophilicity and ion exchange capacity, ImGO with carbethoxy group as the ligand confers the highest OH- conductivity on nanohybrid membrane (up to 1.02 x 10(-2) S cm(-1) at 90 degrees C and 100% RH, about four times of that of CS control membrane). Correspondingly, a fuel cell with such a membrane shows an OCV of 0.71 V and a maximum power density of 75.8 mW cm(-2) at a current density of 298.8 mA cm(-2).