Clustered multi-imidazolium side chains functionalized alkaline anion exchange membranes for fuel cells

Clustered alkyl side chains bearing a string of three imidazolium cations with hexyl spacers are grafted to fluorene-based poly (arylene ether sulfone) successfully. Nanostructure is directly configured within the anion exchange membranes (AEMs) via the novel multi-cation side chains. As confirmed by atomic force microscopy (AFM) and small angle X-ray scattering (SAXS), percolating OH- conducting channels with the size of ionic clusters nearly 20 nm endow the trimPES-0.4 membrane with an excellent ion conductivity in excess of 120 mS cm-1 at 80 °C. Because of the self-assembly of ionic groups, water molecules are compartmentalized into the hydrophilic side chain regions instead of backbones, resulting in advantageous over water management. Together with the lengthened hydrophobic segments, TrimPES-0.2 exhibits superior dimensional stability (12.0%, 30 °C) to conventional mono-cation type AEMs. Furthermore, the novel multi-cation TrimPES-0.4 displays a peak power density of 134.4 mW cm-2 at a current density of 280 mA cm-2. Therefore, these findings suggest that by tuning the distribution of cations, AEMs with well-balanced performance can be made for fuel cell applications.