Cation-Driven Increases of CO 2 Utilization in a Bipolar Membrane Electrode Assembly for CO 2 Electrolysis.

Advancing reaction rates for electrochemical CO 2 reduction in membrane electrode assemblies (MEAs) have boosted the promise of the technology while exposing new shortcomings. Among these is the maximum utilization of CO 2 , which is capped at 50% (CO as targeted product) due to unwanted homogeneous reactions. Using bipolar membranes in an MEA (BPMEA) has the capability of preventing parasitic CO 2 losses, but their promise is dampened by poor CO 2 activity and selectivity. In this work, we enable a 3-fold increase in the CO 2 reduction selectivity of a BPMEA system by promoting alkali cation (K + ) concentrations on the catalyst's surface, achieving a CO Faradaic efficiency of 68%. When compared to an anion exchange membrane, the cation-infused bipolar membrane (BPM) system shows a 5-fold reduction in CO 2 loss at similar current densities, while breaking the 50% CO 2 utilization mark. The work provides a combined cation and BPM strategy for overcoming CO 2 utilization issues in CO 2 electrolyzers.