(503f) Electrochemically Mediated CO2 Sorbent Regeneration: Moving Beyond the Cu-Diamine System

Electrochemical carbon capture has emerged as a viable alternative to the temperature-swing CO2 capture process due to its lower energy demands and greater potential for electrification. This process uses reducing and oxidizing conditions as analogs to the low and high temperatures of used in temperature-swing capture for sorbent regeneration. Electrochemically mediated amine regeneration (EMAR) has been shown to be among the most promising because it can operate at higher concentrations. In the EMAR process uses metal ions, typically copper, to disrupt the N-C carbamate bond of the amine sorbent by competitive inhibition, forming a Cu-N bond and releasing CO2. The metal ion concentrations are controlled electrochemically by electroplating and corrosion reactions to shift between a CO2-capturing state with low metal concentrations and a sorbent-regenerating state with high metal concentrations.

To date, the EMAR process has only been studied using diamine sorbents due to the strong metal-amine coordination achieved by the chelate effect and the established amine-CO2 chemistry. Additionally, experiments to date have prioritized energy consumption as its sole optimization metric, with limited concern for the CO2 absorption rate. In this study, we extend the model to electrochemically mediated sorbent regeneration (EMSR), account for non-amine sorbents that can capture CO2 in the (bi)carbonate forms via pH modulation. We have used a computational aquatic chemistry model of the system to simulate how the system’s energy demand and CO2 absorption rate will change as the sorbent changes, studying the process across the breadth of theoretical bidentate ligands with amines and carboxylic acids as nucleophile sites. We selected this range of compounds to maintain the strong chelate effect that produces the Cu-CO2 competition for the sorbent, using carbonates to represent pH-modulating sorbents without carbamate formation capability. We find that the optimal pKa values for minimizing the energy demand of the system tend towards the pKa values of carbonic acid and bicarbonate, similar to our previous studies of the electrochemical pH-swing method. Amino acids can achieve energy demands and rates similar to that of the diamine system, opening up the opportunity for more water-soluble and environmentally benign amines in the EMSR process. While dicarbonate ligands are capable of CO2 capture in this system, the pKa values and metal coordination strengths achieved by dicarbonates lead to greater energy demands. Current work is ongoing to validate the results experimentally and explore other metal-ligand chemistries.