Alkaline anion exchange membranes based on KOH-treated multilayer graphene oxide

A novel class of alkaline anion exchange membrane (AAEM) is presented, in the form of KOH-modified multilayer graphene oxide paper (GOKOH). Such membranes can be easily fabricated at large scale with varying thickness using conventional filtration techniques, and have high tensile strength (24.5MPa). However, a large degree of swelling is observed. SEM investigations show that the morphology of GO changes after KOH-treatment, whilst XPS measurements and XRD analysis confirm successful chemical modification. The hydrogen gas permeability is several orders of magnitude lower than conventional polymer-based ionomer membranes. The maximum anion conductivity is 6.1mS/cm at 70°C, and the dominant charge carrier is confirmed to be OH− by utilization of anion and proton-conducting blocking layers. The ion exchange capacity is 6.1mmol/g, measured by titration. A water-mediated reverse Grotthuss-like mechanism is proposed as the main diffusion mode of OH− ions. Finally, a prototype AAEM fuel cell is fabricated using a GOKOH membrane, confirming the applicability to real systems. [Display omitted] •A new class of anion exchange membrane was prepared from functionalized multilayer graphene oxide.•Much higher hydrogen gas barrier than conventional fuel cell membranes was measured.•The ionic conductivity is comparable to commercial alkaline membranes.•Dominating ionic species was determined to be OH− via blocking layer measurements.