Preparation of highly conductive anion exchange membranes by introducing dibenzothiophene monomer into the polymer backbone

Abstract

The poly(aryl piperidinium) backbone has outstanding electrical conductivity and chemical stability, which is ideal for the preparation of anion exchange membranes (AEMs). Hence, in this research we prepared a series of high performance AEMs by introducing electron-rich dibenzothiophene (DBT) monomer into poly(aryl piperidinium) polymer backbone. The larger conjugated surface of the DBT monomer and the presence of heteroatoms facilitated intermolecular interactions between the polymers, which induced the generation of highly efficient ion-transport channels within the membranes, as evidenced by atomic force microscopy (AFM) images. The highest molar addition of DBT monomer, QPDBTTP-25 membrane, showed the highest conductivity (190.90 mS cm−1 at 80 °C) while maintaining robust dimensional stability (swelling ratio was 23.66 % at 80 °C). Owing to the advantages of the poly(aryl piperidinium) polymer backbone, the QPDBTTP-25 membrane also exhibited excellent mechanical properties (tensile strength of 53.03 MPa under fully hydrated condition) and durable chemical stability (conductivity retention remained at 93.2% after being immersed in 2 M NaOH solution at 80 °C for 1500 h). The H2/O2 fuel cell test based on QPDBTTP-25 membrane resulted in a peak power density of 384 mW cm−2 at 80 °C.