Reviving the Absorbent Chemistry of Electrochemically Mediated Amine Regeneration for Improved Point Source Carbon Capture

Electrochemically mediated amine regeneration (EMAR) is emerging as a promising electrochemical approach for carbon capture from point sources. In this study, for the first time, the absorbent chemistry of the EMAR process was revived by considering criteria beyond metal-amine complexation. The systematic investigation focused on using secondary amines, which were previously overlooked in EMAR due to limited metal-amine interaction, despite their proven effectiveness in conventional carbon capture processes. The integration of secondary amines— monoethanolamine (MEA), aminomethyl propanol (AMP), and methyldiethanolamine (MDEA)—with the benchmark ethylenediamine (EDA) was thoroughly studied, evaluating their impact on absorption and desorption kinetics and capacities, and electrochemical performance. Among the blends, EDA+MDEA emerged as the top performer, particularly excelling in electrochemical aspects. The charge transfer resistance (RCT) of the deposition reaction, as the rate-limiting step, for the EDA+MDEA blend was reduced by 40% compared to pure EDA, and the heterogeneous electron transfer rate constant (k0) improved threefold. In the bench-scale assessments, the EDA+MDEA blend showed a notable decrease in desorption energetics to 37 kJ/molCO2, marking a 34% reduction compared to the 56 kJ/molCO2 required for pure EDA. This marks the lowest reported energetics for an EMAR process targeting point source carbon capture. This research paves the way for future systematic investigations of a wider range of amine blends for EMAR and eventually the process implementation at larger scales.