Insights into Energetic Penalties in Electrochemical CO2 Separation Systems

While innovative electrochemical approaches continue to emerge for carbon capture, open questions remain regarding the performance characteristics of these nascent concepts. A wide range of energy requirements have been reported; the different sources of performance loss and their relative magnitudes are not yet fully understood, challenging both quantitative comparisons between devices and identification of performance improvement pathways. Herein, we develop a mathematical framework to evaluate the energetics of four-stage electrochemical separation systems in which soluble capture chemistries are activated and deactivated in an electrochemical reactor, and bind and release carbon dioxide (CO2) in separate units. Specifically, we construct a dimensionless electrochemical reactor model, derive key groups associated with thermodynamics, kinetics, ohmic resistance, and mass transport, and, subsequently, evaluate their impact on energetic penalties. We also discuss the use of this model for exploring different performance improvement pathways. Ultimately, this work seeks to facilitate understanding of the interplay between material properties, operating conditions, and energy requirements.