Integrated Materials for Ion Transport Management in Anion Exchange Membrane Electrolyzers

Abstract

Electrochemical CO₂ separation systems leveraging anion exchange membranes (AEMs) offer significant energetic advantages over traditional bipolar membrane electrodialysis (BPMED), but suffer from hydroxide crossover, which reduces current efficiency (CE) and system performance. This work explores the transport dynamics of carbonate and hydroxide ions in AEM systems and introduces a hybrid PES-AEM bilayer membrane architecture to mitigate hydroxide crossover while preserving sufficient CO₂ recovery. We demonstrate that the bilayer system achieves a reduced relative transport factor (R = 1.4) and enables up to 3.8x improvement in CE compared to conventional AEM systems at realistic capture conditions. Further analysis reveals that transport properties in the least conductive domain of a multi-membrane system dominate overall behavior, allowing non-selective, low-conductivity materials such as porous PES to reduce hydroxide crossover effects. This study outlines key membrane material parameters influencing relative ionic transport and highlights the potential of hybrid architectures to unlock energy-efficient CO₂ electrochemical regeneration for direct air capture (DAC) integration.