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

Abstract

AbstractReducing 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.