Photo-cross-linked poly(N-allylisatin biphenyl)-co-poly(alkylene biphenyl)s with pendant N-cyclic quaternary ammonium as anion exchange membranes for direct borohydride/hydrogen peroxide fuel cells

Abstract The slightly crosslinked poly(N-allylisatin biphenyl)-co-poly(alkylene biphenyl)s (PIB-co-PAB) based anion exchange membranes are prepared by super-acid catalyst polycondensation and thiol-ene click chemistry in situ. The hydrophilic crosslinked structure improves the hydroxide conductivity due to enhanced the water uptake and well-developed microphase separation. Furthermore, the introduction of N-spirocyclic quaternization ammonium groups promotes the chemical stability of the prepared membranes. Among them, the crosslinked PIB-co-PAB membrane with high ion exchange capacity exhibit high ion conductivity of 24.7 and 39.1 mS·cm−1 at 30 °C for chloride and hydroxide ionic conduction, respectively. Moreover, it possesses an acceptable alkaline stability, which remains the 65.19% of original hydroxide conductivity after storage in 1 M NaOH solution at 80 °C for 1000 h. Meanwhile, the crosslinked membranes exhibit lower permeability for borohydride anion than un-crosslinked membranes. Additionally, the peak power density of direct borohydride/hydrogen peroxide fuel cells using the crosslinked membrane as separator is 76.1 mW·cm−2 at 149.2 mA·cm−2, which is higher than un-crosslinked membranes (17.3 mW·cm−2 at 48.2 mA·cm−2) Therefore, all the results reveal that the prepared free aryl-ether bonds linkage membranes with hydrophilic crosslinked structure provide potential application in fuel cells.