Revolutionizing Carbon Capture: Scientists Unveil New CO2 Reaction Pathways

HKUST researchers discovered how CO₂ reacts in supercritical water, identifying pyrocarbonate ions as key intermediates. Their work highlights nanoconfinement’s role in chemical processes and offers new directions for carbon sequestration technologies.

A research team led by Associate Professor Ding Pan from the Departments of Physics and Chemistry at the Hong Kong University of Science and Technology (HKUST), in collaboration with Professor Yuan Yao from the Department of Mathematics, has uncovered key insights into the reaction mechanisms of carbon dioxide (CO₂) in supercritical water.

These findings are vital for advancing our understanding of CO₂ mineralization and sequestration processes in both natural and engineered systems, as well as the deep carbon cycle within the Earth’s interior. This research provides a foundation for developing innovative carbon sequestration technologies in the future. The study was published in the Proceedings of the National Academy of Sciences (PNAS).

The dissolution of CO₂ in water and its subsequent hydrolysis reactions are key processes for effective carbon capture and mineralization storage, playing a significant role in carbon sequestration to mitigate global warming. Prof. Pan’s team developed and applied first-principles Markov models to reveal the reaction mechanisms of CO₂ with supercritical water in both bulk and nanoconfined environments.

Surprising Role of Nanoconfinement in CO₂ Reactions

They discovered that pyrocarbonate (C₂O₅^2-) is a stable and important reaction intermediate in nanoconfined environments, which had been previously overlooked because pyrocarbonate is highly unstable and decomposes rapidly in aqueous solutions. The unexpected appearance of pyrocarbonate is related to the superionic behavior of the confined solutions.

Additionally, they found that carbonation reactions involve collective proton transfer along transient water chains, which exhibits concerted behavior in bulk solutions but proceeds stepwise under nanoconfinement. This study demonstrates the great potential of first-principles Markov models in elucidating complex reaction kinetics in aqueous solutions.

An Innovative Computational Approach to Reaction Pathways

“Our innovative approach has enabled us to discover a new pathway for CO₂ dissolution involving pyrocarbonate ions,” said Prof. Chu Li, Research Assistant Professor from the Department of Physics. “Our efficient computational method does not rely on prior knowledge and can automatically identify reaction pathways without human bias, revealing unknown reaction mechanisms based on the first principles of physics.”

Prof. Ding Pan added, “Our method employs unsupervised learning techniques to reveal the importance of large oxocarbons in aqueous reactions under extreme conditions, while also demonstrating that nanoconfinement can be an effective strategy for regulating chemical processes. These findings are expected to provide new directions for future carbon sequestration technologies.”

Reference: “Unveiling hidden reaction kinetics of carbon dioxide in supercritical aqueous solutions” by Chu Li, Yuan Yao and Ding Pan, 30 December 2024, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2406356121

The research was supported by the Hong Kong Research Grants Council, the Croucher Foundation, and the Excellent Young Scientists Fund of the National Natural Science Foundation of China. Part of the computational work was carried out on the Tianhe-2 supercomputer at the National Supercomputer Center in Guangzhou.

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