High performance anion exchange membrane containing large, rigid branching structural unit for fuel cell and electrodialysis applications

Highly conductive and robust anion exchange membrane (AEM) is the key for development of alkali fuel cell and electrodialysis. We herein report novel, branched polyarylpiperidinium AEMs containing 1,3-dicarbazole-9-ylbenzene (DCB) unit. As a larger, more rigid branching unit relative to the conventional one, DCB can create higher fraction of free volume in the AEM, induce more significant microphase separation and better restrict water swelling of the membrane. The prepared qTPDCB-5.5 AEM exhibited an excellent hydroxide conductivity (175.3 mS cm⁻¹) and a low swelling ratio (21 %) at 90 °C; when soaked in aqueous sodium hydroxide solution (2 mol/L, 80 °C) for 1000 h, qTPDCB-5.5 showed a high conductivity retention (96.5 %). Its hydrogen/oxygen fuel cell reached an impressive peak power density (1.83 W cm⁻²), and the qTPDCB-5.5 AEM did not experience appreciable structural decomposition after the cell worked at 0.2 A cm⁻² for 230 h (including >100 h intermittent discharge). Owing to its high conductivity and swelling resistance, the qTPDCB-5.5 membrane also showed good performance in electrodialysis, and gave rise to low energy consumption (2.72 kWh kg⁻¹) when used for desalinating 0.1 M NaCl solution. This work highlights the importance and provides the methodology of incorporating large, rigid branching unit in the structure of high performance AEM for fuel cell and electrodialysis applications.