We've updated our Privacy Policy to make it clearer how we use your personal data. We use cookies to provide you with a better experience. You can read our Cookie Policy here.


Aqueous Amino Acid’s Potential for Direct Air Capture of CO2 Decoded

Clouds spelling CO2 in the sky.
Credit: Matthias Heyde / Unsplash.
Listen with
Register for free to listen to this article
Thank you. Listen to this article using the player above.

Want to listen to this article for FREE?

Complete the form below to unlock access to ALL audio articles.

Read time: 2 minutes

Scientists at the Department of Energy’s Oak Ridge National Laboratory have made a significant stride toward understanding a viable process for direct air capture, or DAC, of carbon dioxide from the atmosphere. This DAC process is in early development with the aim of achieving negative emissions, where the amount of carbon dioxide removed from the envelope of gases surrounding Earth exceeds the amount emitted.

The recently published research focused on the foundational steps of carbon dioxide sequestration using aqueous glycine, an amino acid known for its absorbent qualities. By combining a series of advanced computational methods, the scientists probed less-explored dynamic phenomena in liquid solutions related to the rate at which carbon dioxide can be captured.

Want more breaking news?

Subscribe to Technology Networks’ daily newsletter, delivering breaking science news straight to your inbox every day.

Subscribe for FREE

“Chemical reactions in water are complicated, especially when the motion of water molecules plays a big role,” said Santanu Roy, who designed the computational investigation with colleague Vyacheslav Bryantsev. “Water molecules and chemicals engage in something similar to a coupled dance that can marginally or significantly slow the reaction. Understanding these dynamic interactions, known as nonequilibrium solvent effects, is essential to getting the full picture of how reactions work and how fast they happen.”

The researchers discovered that when examining the rate at which carbon dioxide is absorbed, focusing solely on the free energy barrier — the energy threshold that must be overcome for a system to transition from one state to another — is an oversimplification that does not provide the full picture. This incomplete approach can lead to an inaccurate understanding of reaction kinetics, the factors that influence the speed at which a reaction occurs.

“We employed a more complete approach that considers the influence of water on the motion along the reaction path, and the outcome was intriguing,” Bryantsev said. “The initial step, where glycine interacts with carbon dioxide, is nearly 800 times slower compared with the next step, where a proton is released to ultimately form a mixture of product state for holding the absorbed carbon dioxide. Strikingly, the free energy barrier remains constant for both steps, and so this different perspective truly sets the speed of these two critical stages apart and offers a pathway to boost the efficiency of carbon dioxide absorption and separation.”

The extensive ab initio molecular dynamics simulations used in this study were still limited by their short time and length scales and high computational costs in representing the chemical reactions.

“For future projects, we intend to combine the emerging machine-learning approach with highly accurate simulations and develop interatomic interaction potentials based on deep neural networks. This will allow us to perform molecular simulations with high accuracy at large scales with significantly reduced computational costs,” said Xinyou Ma, who carried out the simulations.

Roy added: “While we have portrayed a molecular-level kinetics picture of carbon dioxide capture by aqueous amino acids, accessing large length and time scales through the use of the machine-learning approach will help us understand the effects of macroscopic factors such as temperature, pressure and viscosity on DAC and how these effects are related to the attained molecular picture.”

Overall, the study’s findings shed light on the intricate workings of DAC and emphasize the vital role of kinetics, thermodynamics and molecular interactions in removing carbon dioxide from the atmosphere by aqueous amino acids. As these mechanisms become more accurately understood, the prospect of deploying a large-scale DAC technology will become more feasible. Worldwide, several different DAC projects are in various stages of research, testing and development.

Reference: Ma X, Bryantsev VS, Roy S. An ab initio free energy study of the reaction mechanism and rate-limiting steps of CO2 capture by aqueous glycine. Cell Rep Phys Sci. 2023;4(11):101642. doi: 10.1016/j.xcrp.2023.101642

This article has been republished from the following materials. Note: material may have been edited for length and content. For further information, please contact the cited source.