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Van 't Hoff Institute for Molecular Sciences Van 't Hoff Institute for Molecular Sciences

How amines and electrodes affect CO2 conversion

Studying electrochemical CO2 reduction in an integrated system for carbon capture and utilisation

5 November 2024

In a paper in Nature Communications, chemists at the Van ‘t Hoff Institute for Molecular Sciences led by Dr Amanda Garcia report a crucial aspect of the electrochemical conversion of carbon dioxide in an integrated system for carbon capture and utilisation (CCU). They investigated how the conversion outcome depends on the used amines and electrodes, underpinning the importance of optimizing amines and electrode materials to enhance CCU efficiency.
The study focused on the amines monoethanolamine (MEA) and 2-amino-2-methyl-1-propanol (AMP), see A. Distinct electron transfer mechanisms were established: inner-sphere (Cu, bond formation) and outer-sphere (Pb, interaction), see B. Below, the overall chemical reaction of bicarbonate production (HCO3−) in the presence of amines and CO2 is depicted (C). Image: Nat Commun / HIMS.

The use of amine-based solvents is key in many integrated systems for capture and subsequent electrochemical conversion of CO₂. Using in situ spectroscopy, a powerful tool for revealing reaction mechanisms, the researchers were able to pinpoint substantial differences in the reaction mechanisms between two types of amines on different electrode materials. The study revealed how the use of monoethanolamine (MEA) on copper electrodes leads to proton shuttling, which hinders CO₂ reduction. On the other hand, the researcher show how the use of 2-amino-2-methyl-1-propanol (AMP) on lead electrodes can substantially promote CO₂ reduction.

The research thus demonstrates how to optimize the choice of amines and electrode materials to promote the selective conversion of CO₂. These results are relevant to industrial application, advancing the conversion of CO₂ emissions into valuable products.

Abstract, as published with the paper

Carbon capture and utilization (CCU) technologies present a promising solution for converting CO2 emissions into valuable products. Here we show how amines, such as monoethanolamine (MEA) and 2-amino-2-methyl-1-propanol (AMP), influence the electrochemical CO2 reduction process in an integrated CCU system. Using in situ spectroscopic techniques, we identify the key roles of carbamate bond strength, proton shuttling, and amine structure in dictating reaction pathways on copper (Cu) and lead (Pb) electrodes. Our findings demonstrate that on Cu electrodes, surface blockage by ammonium species impedes CO₂ reduction, whereas on Pb electrodes, proton shuttling enhances the production of hydrocarbon products. This study provides additional insights into optimizing CCU systems by tailoring the choice of amines and electrode materials, advancing the selective conversion of CO₂ into valuable chemicals.

Paper details

Bruggeman, D.F., Rothenberg, G. & Garcia, A.C. Investigating proton shuttling and electrochemical mechanisms of amines in integrated CO2 capture and utilization. Nat Commun 15, 9207 (2024). DOI: 10.1038/s41467-024-53543-4