Doped double spirocyclic cationic POSS for nanocomposite anion exchange membranes with high conductivity and robustness

Organic-inorganic hybridization methods are receiving increasing attention as a method that can improve the performance of anion exchange membranes (AEMs) in a simpler and more effective way. Here, by selecting polyhedral oligomeric silsesquioxane (POSS) with good mechanical and thermal properties as inorganic fillers. Successful introduction of N-spirocyclic cations with bifunctional groups onto POSS yielded MDSU-poss. subsequently, we doped them into qPTP-IC-O-9% membranes as fillers in different ratios to obtain a series of composite membranes. High-density cations introduced by POSS with simultaneous organic-inorganic frameworks effectively inhibit membrane over-swelling. As a result, the membrane is able to achieve high ionic conductivity with the assurance of reasonable dimensional stability. At 80 °C, the 15 % MDSU-poss/qPTP-IC-O membrane achieved the ionic conductivity of 168.6 mS cm−1 at low SR with the peak power density of 431 mW cm−2. In addition, the mechanical properties of the composite membranes were all greatly improved due to the organic cations attached to the POSS with good affinity, contributing to the tensile strength of the 15 % MDSU-poss/qPTP-IC-O membrane of 57.4 MPa. The membrane was finally immersed in 3 M NaOH solution for 1032 h and still maintained 89.3 % of the starting ionic conductivity.