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Greenhouse Gases

Electrochemical process cuts the energy use of amine-based carbon capture

Using the right combination of ions in an electrochemical cell enables reversible capture and release of CO2

by Prachi Patel, special to C&EN
September 11, 2023 | A version of this story appeared in Volume 101, Issue 30


Image shows a cathode on the left side and a metal foil anode on the right, with multiple chemical structures in the middle, to represent the action of the new electrochemical cell that can absorb carbon dioxide.
Credit: Adapted fromACS Cent. Sci.
Charging the electrochemical cell injects metal cations that trigger a reaction that results in the electrolyte taking up carbon dioxide.

Carbon capture, whether from power plant flues or directly from air, relies mostly on amine-based sorbents to capture carbon dioxide. Separating the CO2 and amines requires heating the sorbents—typically by burning fossil fuels.

Researchers have designed an electrochemical process that can trap and release CO2 in liquid amine sorbents (ACS Cent. Sci. 2023, DOI: 10.1021/acscentsci.3c00692). The process uses less energy than conventional methods but gathers the same amount of CO2 by weight. Using renewable electricity would “make the carbon capture process more sustainable,” says Fang-Yu Kuo, a chemical engineering graduate student at the Massachusetts Institute of Technology.

The new devices run at ambient temperatures and pressures, making them smaller and cheaper than the reactors used to heat amines for CO2 release. Researchers have previously made electrochemical devices based on quinones, or that swing the pH of alkaline solutions.

The researchers combined electrochemical CO2 capture and release with the strong amine sorbents already in use in the field. The team made an electrochemical cell from a zinc anode, a Prussian White cathode made of potassium, carbon, iron, and nitrogen, and an electrolyte containing ethoxyethylamine.

Charging the cell releases potassium ions into the electrolyte. This triggers CO2 from air or exhaust passed through the cell to react with the amine, forming carbamic acid. Zinc cations enter the electrolyte during discharge, and the reverse reaction releases CO2 from the carbamic acid to form carbamate.

Jianbing Jiang, a chemist at the University of Cincinnati, commends the team’s systematic investigation, which “paves the way towards more efficient CO2 capture and utilization,” he says.



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