Evaluation of a Second-Generation Bulky Cation for Anion Exchange Membranes

Abstract

Researchers worldwide have developed bulky cations for incorporation into anion exchange membranes (AEMs) used in energy transfer and storage devices. The bulky cations increase chemical stability by attaching electron-donating groups to the central cation. In this work, we compared the performance of the bulky tris(2,4,6-trimethoxy phenyl) phosphonium cation (TPQP) to the much smaller benchmark trimethylammonium cation (TMA) commonly utilized in alkaline fuel cells. The TPQP cation exhibits higher thermal and chemical stability than the TMA cation. Polyphenylene oxide (PPO) membranes functionalized with TPQP cation show comparable anion1ic conductivity values to similar membranes functionalized with TMA cation. Mechanical testing of 15 μm membranes of the tris(2,4,6-trimethoxy phenyl) phosph- onium functionlized PPO (PPO-TPQP) indicates that in order to meet the demands of commercial applications, Young’s modulus will need to be reduced and membrane elongation need to be increased.