Promising medium can capture and convert carbon dioxide, while regenerating itself for reuse - Energy & Green Tech

Feedstock-producing route comparison and tandem amine scrubbing and CO₂ electrolysis. a, Tandem amine scrubbing and CO₂ electrolysis scheme (also reported as reactive CO₂ capture). b, Sequential CO₂ capture and gas-phase CO₂ electrolysis scheme. c, Industrial reverse water gas shift reaction (RWGS) scheme. Credit: Li et al. (Springer, Nature Energy, 2025). DOI: 10.1038/s41560-025-01869-8.

Over the past decades, energy researchers have developed various promising solutions to limit the emission of greenhouse gases and source fuels or other chemicals more sustainably. These solutions include so-called carbon capture technologies and electrolyzers, devices that can capture carbon dioxide (CO₂) and convert it into other valuable products, such as carbon monoxide (CO), methanol (CH₃OH), methane (CH₄) and various other compounds.

Some recently introduced solutions for converting CO₂ into compounds that can be used as fuels or in industrial settings have achieved promising results. However, most of these devices only work if CO₂ is purified (i.e., separated from other gases, contaminants and impurities). This additional purification step reduces the devices' efficiency and can increase costs associated with their deployment, preventing their large-scale implementation.

An alternative method for the capture and conversion of CO₂, known as reactive CO₂ capture, could be more efficient and scalable than conventional approaches. This method combines the capture and conversion of CO₂ in a single process, relying on compounds containing nitrogen (i.e., amine-based absorbents) to directly convert captured CO₂ into desired compounds via electrochemical reactions.

Researchers at RMIT University, University of Auckland and other institutes recently carried out a study aimed at evaluating the efficiency of various amine-based absorbers for reactive CO₂ capture. Their paper, published in Nature Energy, suggests that the cyclic amine piperazine outperforms other amines, boosting the energy-efficiency of reactive CO₂ capture processes.

"Transforming CO₂ into valuable products presents a promising route for reducing emissions across various industry sectors," wrote Peng Li, Yu Mao and their colleagues in their paper. "However, conventional methods, including sequential CO₂ electrolysis or reverse water–gas shift reaction, depend on energy-intensive CO₂ purification; while emerging reactive CO₂ capture strategies still face challenges in designing optimal system components that enable efficient electrochemical regeneration without compromising catalytic performance.

"We systematically screen a broad library of amine-based absorbents to establish a design rationale for tandem amine scrubbing and CO₂ electrolysis."

As part of their study, Li, Mao and their colleagues used a range of amine chemicals to capture CO₂ and convert it into CO. They found that piperazine was the most effective for reactive CO₂ capture, yielding one of the highest energy-efficiencies reported to date.

"We identify piperazine as an optimal capture medium and show that its carbamate form can be directly reduced using a nickel single-atom catalyst," wrote the authors. "This charge-neutral intermediate facilitates spontaneous adsorption, rapid transport and efficient C–N bond cleavage, enabling stable carbon monoxide production alongside in situ amine regeneration. The process achieves an energy efficiency of ~48.8 GJ per tonne CO, offering a scalable and energy efficient pathway towards carbon-neutral chemical feedstocks."

Piperazine, the amine identified by the researchers, was found to regenerate itself automatically, which could reduce the waste and costs associated with the reactive capture of CO₂. Other research teams could soon draw inspiration from the team's findings and set out to further explore the potential of piperazine for the capture and direct conversion of CO₂ into CO, both in laboratory and real-world settings. In the future, the recent work by Li, Mao and their colleagues could contribute to the reliable deployment of reactive CO₂ capture devices on a large-scale. 

by Ingrid Fadelli, Phys.org

edited by Gaby Clark, reviewed by Robert Egan 

Source:  Promising medium can capture and convert carbon dioxide, while regenerating itself for reuse