Modeling the performance of high carbon concentration electrolytes at CO2 electrolysis cathodes*

One major barrier to the commercialization of low-temperature CO2 electrolysis is the so-called “carbonate problem”, where CO2 reacts with hydroxide ions at the cathode to form carbonate. This process contributes to both carbon and energy losses, and proposed solutions have not been able to recover the carbon without an excessive energy penalty in the form of high cell voltage. Our approach uses a high inorganic carbon concentration electrolyte to operate at a high pH while minimizing the driving force for carbonate formation. These electrolyte conditions are characterized by multiple coupled equilibria in a high bulk concentration environment and have rarely been studied. We have built a computational model for the cathode that couples electrochemical reactions with homogeneous reactions, ion transport using the Nernst-Planck equation, and gas transport. In particular, we investigated the coupling between gaseous and liquid phases to determine how CO2 dissolves into various electrolyte compositions. We focused on performance driven optimization considering multiple figures of merit and will present a sensitivity analysis to major aspects of the system.