Anion exchange membranes with "rigid-side-chain" symmetric piperazinium structures for fuel cell exceeding 1.2 W cm−2 at 60 °C

Developing anion exchange membranes (AEMs) having high hydroxide conductivity, swelling resistance and excellent alkaline stability is a challenge for fuel cells now. Herein, a universal and controllable approach of grafting rigid side chain is first proposed to construct connected ion transport nano-channels. A new route is also provided to prepare AEMs with stable symmetric saturated heterocyclic amomium. The rigid side chain is introduced onto poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) by the Friedel-Crafts acylation with 4-fluorobenzoyl chloride and subsequent reaction between phenyl fluoride and secondary amine of 1-methylpiperazine. Then the terminal piperazinium is produced by the reaction between tertiary amine of 1-methylpiperazine and methyl iodide. Rigid branches expand free volume to construct connected ion transport nano-channels, leading to excellent conductivity (108 mS cm−1 at 60 °C) that is higher than those of other reported symmetric heterocyclic amomium functionalized AEMs (33–89 mS cm−1 at 60 °C). Due to the high conductivity, the H2/O2 cell employing this membrane achieves one of the highest peak power densities (1210 mW cm−2 at 2600 mA cm−2) so far. In addition, the IEC of the membrane remains constant after testing in 1 M NaOH at 60 °C over 500 h.