Membrane Engineering Reveals Descriptors of CO2 Electroreduction in an Electrolyzer

Abstract

Anion exchange membranes (AEMs) and ionomers are keys for electrochemical CO₂ reduction (eCO₂R), but their development and multiple roles have not been intensively investigated. This study demonstrates HQPC-tmIM, a polycarbazole-based anion-conducting material, as a commercially viable AEM and reveals through multiphysics model simulation key descriptors governing eCO₂R by exploiting the extraordinary membrane properties of HQPC-tmIM. The mechanical/chemical stability of HQPC-tmIM showed superior eCO₂R performance in a membrane electrode assembly electrolyzer (MEA) in comparison to a commercial AEM (Sustainion). The CO partial current density (j_CO) of ?603 mA cm^–2 on HQPC-tmIM MEA is more than twice that of Sustainion MEA and is achieved by only introducing HQPC-tmIM AEM and binder. The mutiphysics model revealed that the well-constructed membrane morphology of HQPC-tmIM leads to the outstanding membrane conductivity, and it enables high j_CO through the facilitated charge transfer in overall reactions. This research suggests guidelines for developing a commercially viable AEM and ionomer for eCO₂R.