Improving the proton conductivity of graphene oxide membranes by intercalating cations

Graphene oxide (GO) membrane has gained increasing attention because of its extraordinary physical and chemical properties and high proton conductivity. GO is rich in oxygenated functional groups, which can support proton transportation. However, pristine GO is unstable at high temperatures due to the removal of oxygen functional groups, resulting in a decrease in the interlayer distance of stacked GO nanosheets. Hence, we propose a modification of GO membranes via the intercalation of cations to enhance the proton conductivity. Modified self-standing GO membranes with Al 3+ and La 3+ were fabricated by a vacuum filtration method. They exhibited a larger distance of the interlayer that serves as proton hopping pathways. Furthermore, the modified GO membrane showed a higher proton conductivity than a pristine GO membrane even at 80 °C, as confirmed by Electrochemical Impedance Spectroscopy. The results demonstrate that intercalating cations in between GO nanosheets is effective in improving the practical feasibility of proton conducting GO membranes.