Performance comparation of MEA and EDA in electrochemically-mediated amine regeneration for CO₂ capture

Electrochemically-mediated amine regeneration (EMAR) for CO₂ capture was recently developed as a promising substitute for conventional amine-based CO₂ capture by avoiding the amine thermal regeneration process. A suitable solvent is significant for the overall performance and the scale-up of the EMAR system. However, there is currently a lack of comprehensive solvent comparison methods. In this work, a systematic comparison was conducted to elucidate the absorption and desorption behavior of the most discussed monoethanolamine (MEA) and ethylenediamine (EDA) in the EMAR process. Firstly, the CO₂ absorption performance was compared by considering the CO₂ absorption capacity, absorption rate, and coordination ability separately. Subsequently, the performance of absorbents was compared from the perspective of thermodynamics. Results indicated that the complex of Cu(II)-EDA shows higher stability which means it is more competitive than MEA in releasing the absorbed CO₂ in the EMAR process. Then, the electrochemical behaviors comparison of MEA and EDA shows that the electrochemical reactions in EDA solvent are simpler and easier to occur, but the poor diffusion performance of reactive ions in EDA hinders its scale-up application. Finally, the CO₂ desorption performance in MEA and EDA was carefully studied. A competitive and practically instructive desorption energy consumption of 42.4 kJ_e/mol CO₂ with 300 A/m² current density was obtained in EDA solvent. Overall, compared with MEA, EDA is more recommended to be used as an absorbent in the EMAR system.