Anion exchange membrane with well-ordered arrays of ionic channels based on a porous anodic aluminium oxide template

Abstract

A novel nanofibrous asymmetric framework based on a porous anodic aluminium oxide template has been proposed for the construction of ionic channels in a quaternized polysulfone anion exchange membrane (A-QAPSF AEM). The nanofibrous array layer (60 µm in length and ~ 400 nm in fibre diameter) provides good water sorption and through-plane pathways for effective hydroxide ion transport, whereas the dense layer (50 µm) suppresses fuel penetration and acts as a mechanical support for the nanofibres. The vertically aligned nanofibres in nanofibrous array layers contact with each other closely to form well-ordered arrays of ionic channels, leading to a remarkable twofold enhancement of the through-plane conductivity over that of a traditional homogeneous membrane (QAPSF) (7.11 vs. 2.19 mS cm− 1) at 25 °C and comparable in-plane conductivity. The micro-scale voids among the nanofibrous arrays in the A-QAPSF could function as reservoirs for water storage and cushion the dimensional change, simultaneously achieving a higher water uptake (46.0%) and lower swelling ratio (5.5%). This nanofibrous asymmetric framework represents a promising method to build up the aligned ionic channels along the thickness direction of AEMs.