Why Membranes Matter: Ion Exchange Membranes in Holistic Process Optimization of Electrochemical CO₂ Reduction

Abstract

Reducing carbon dioxide to value‐added chemicals by electrolysis is a promising strategy to substitute fossil‐based processes. Research on CO2 electrolysis has vastly progressed, focusing on catalysis and electrode design, leaving an essential question on the central part of the electrolyzer: Which type of ion exchange membrane is best suited for CO2 electrolysis from an economic perspective? To address this question, holistic process optimization of CO2 reduction and product purification is applied. The findings demonstrate that CO2 electrolysis with an anion exchange membrane shows competitive production costs for CO of 796 €/tCO, outperforming cation exchange and bipolar membranes. Unlike often described, the CO2 pumping effect does not significantly impair the economics but offers an efficient indirect regeneration of dissociated CO2. Furthermore, the results emphasize selective reduction of CO2 rather than co‐electrolysis of CO2 and H2O. While pointing to a positive economic perspective, life‐cycle assessment highlights the need to minimize CO2 emissions related to electricity consumption and incomplete CO2 utilization.

Bipolar Membrane with Porous Anion Exchange Layer for Efficient and Long‐Term Stable Electrochemical Reduction of CO2 to CO

“…To find this optimum, several studies investigated the separation cost and concluded that the single‐pass conversion should only be optimized, if the cell voltage increase stays below 0.2 V and the CO Faradaic efficiency does not decrease significantly. [ 1,35 ] Hence, for our cell the 5 mL min −1 flow rate might be the optimum with a FE CO close to 90% and a single‐pass conversion of 49%.…”

“…From a techno‐economic point of view, carbon monoxide (CO), ethylene, and formic acid are seen as most viable products. [ 1–3 ] Electrolyzers for the electrochemical reduction of CO 2 to CO are the most mature technology compared to other products, showing high product selectivity above 90% and partial current densities for CO of more than 1 A cm −2 . [ 4–7 ] However, the ideal electrolysis cell design is still under debate with several different cell architectures currently being investigated.…”

“…[ 4–7 ] However, the ideal electrolysis cell design is still under debate with several different cell architectures currently being investigated. [ 1,7–9 ]…”

“…[ 9 ] The recovery of the CO 2 from the anode gas stream increases the complexity, cost as well as the energy demand of the electrolyzer setup. [ 1,16 ]…”

Facet Engineering of Copper for Product Specific CO2 Electroreduction

“…The lifetime of an electrolysis cell configuration is a crucial factor when evaluating the feasibility of using electrolysis technology for industrial applications. Several key components of the cell, including the electrodes, membrane type, and other materials, influence its longevity and economic viability. − Rumayor and co-workers conducted a significant techno-economic study focused on the electroconversion of carbon dioxide (CO 2 ) into formate, a process that carries substantial implications for sustainable energy and environmental management. Their research delves into comparing this innovative electroconversion approach to the conventional method of formate production, which involves the hydrolysis of methyl formate.…”