High Indirect Energy Consumption in AEM-Based CO(2) Electrolyzers Demonstrates the Potential of Bipolar Membranes

[Image: see text] Typically, anion exchange membranes (AEMs) are used in CO(2) electrolyzers, but those suffer from unwanted CO(2) crossover, implying (indirect) energy consumption for generating an excess of CO(2) feed and purification of the KOH anolyte. As an alternative, bipolar membranes (BPMs) have been suggested, which mitigate the reactant loss by dissociating water albeit requiring a higher cell voltage when operating at a near-neutral pH. Here, we assess the direct and indirect energy consumption required to produce CO in a membrane electrode assembly with BPMs or AEMs. More than 2/3 of the energy consumption for AEM-based cells concerns CO(2) crossover and electrolyte refining. While the BPM-based cell had a high stability and almost no CO(2) loss, the Faradaic efficiency to CO was low, making the energy requirement per mol of CO higher than for the AEM-based cell. Improving the cathode–BPM interface should be the future focus to make BPMs relevant to CO(2) electrolyzers.