A poly(naphthalene-co-biphenyl piperidinium)-based highly conductive and durable anion exchange membrane for electrochemical energy devices

Abstract

Anion exchange membranes (AEMs) play a pivotal role in diverse electrochemical energy systems, including water electrolyzers, fuel cells, and redox flow batteries. However, conventional AEMs are often hindered by inadequate ion conductivity and chemical instability, limiting their performance. In this study, we introduce a poly(naphthalene-co-biphenyl piperidinium) (QPNBM)-based AEM and ionomer for electrolyzer and flow battery applications. The QPNBM membrane demonstrates outstanding hydroxide ion conductivity (197 mS cm⁻¹) and chloride ion conductivity (112.4 mS cm⁻¹) at 100 °C, coupled with excellent ex situ durability of 1500 h in 1 M KOH at 80 °C. In a water electrolysis setup, using Pt/C and IrO₂ catalysts with a 1 M KOH solution, the QPNBM membrane incorporating a fluorinated poly(carbazole-co-biphenyl piperidone) ionomer achieved a peak current density of 1.82 A cm⁻² at 60 °C and 2.4 V. In aqueous organic redox flow batteries, the QPNBM membrane demonstrated outstanding performance, with an energy efficiency of ∼77% and exceptional capacity retention (>99.56% over 50 cycles) at a current density of 10 mA cm⁻². These findings underscore the potential of the QPNBM-based ionomer as a high-performance membrane material for AEM-based electrochemical energy systems.