Ethylene Production from Carbonate Using a Bipolar Membrane Electrolysis System

Abstract

Electrochemical CO 2 reduction has attracted significant interest as a pathway for achieving a carbon-neutral society. However, conventional gas-phase CO 2 electrolysis cell configurations often face challenges like low CO 2 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 CO 2 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 CO 2 and facilitate its conversion into ethylene (C 2 H 4 ), using Cu−Ag catalysts and carbon capture solutions such as potassium carbonate (K 2 CO 3 ). Bench-top flow cell system testing using an optimized Cu−Ag electrocatalyst demonstrates that the conversion of CO 2 to C 2 H 4 reaches 10% Faradaic efficiency, corresponding to a partial current density of 10 mA/cm 2 . During all tests, the BPM-MEA electrolysis cell also maintained approximately 0% CO 2 concentration in the outlet over 24 h. Operating at elevated temperatures, such as 50 °C, has shown promising results in our exploration, demonstrating improved C 2 H 4 Faradaic efficiency and current densities. Lastly, we examine the feasibility of this combined CO 2 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.

Integrated carbon capture and CO production from bicarbonates through bipolar membrane electrolysis

“…Recently, numerous research groups have conducted comprehensive studies on (bi)carbonate electrolysis in the BPM–MEA systems, including catalyst designs 17–20 and optimization of local electrolysis environments. 5,11–14,21–23 These treatments can effectively control the mass transfer of reactants, such as bicarbonates/carbonates, in-situ generated CO 2 , and protons at the catalyst layer, which can enhance CO 2 RR activity.…”