Ethylene Production from Carbonate Using a Bipolar Membrane Electrolysis System

Abstract

Electrochemical CO2 reduction has attracted significant interest as a pathway for achieving a carbon-neutral society. However, conventional gas-phase CO2 electrolysis cell configurations often face challenges like low CO2 utilization efficiency due to carbonate crossover, and costly integration with carbon capture systems. The membrane electrode assembly (MEA) electrolysis cell configuration involving a bipolar membrane (BPM) has been recently spotlighted as this system can directly release CO2 stored in carbonate solutions using a pH swing process driven by water dissociation within the BPM. Here, we assess the reactor’s capacity to liberate CO2 and facilitate its conversion into ethylene (C2H4), using Cu-Ag catalysts and carbon capture solutions such as potassium carbonate (K2CO3). Bench-top flow cell system testing using an optimized Cu-Ag electrocatalyst demonstrates that the conversion of CO2 to C2H4 reaches 10% Faradaic efficiency, corresponding to a partial current density of 10 mA/cm2. During all tests, the BPM-MEA electrolysis cell also maintained approximately 0% CO2 concentration in the outlet over 24 h. Operating at elevated temperatures, such as 50 °C, has shown promising results in our exploration, demonstrating improved C2H4 Faradaic efficiency and current densities. Lastly, we examine the feasibility of this combined CO2 generation and conversion reactor architecture and estimate the potential energy and process efficiencies achievable using the BPM-MEA system. While the BPM-MEA system offers innovative solutions for carbon capture and conversion, continued research and optimization are imperative to fully harness its potential for a sustainable future.