Researchers at Lawrence Livermore National Laboratory (LLNL), in collaboration with the Georgia Institute of Technology, have made a significant breakthrough in understanding the impact of carbon dioxide (CO2) on the stability of amine-functionalized porous solid materials, a crucial component in Direct Air Capture (DAC) carbon-capture technologies.
This new research, published in the Journal of the American Chemical Society and featured on the journal cover, sheds light on the complex interactions between CO2 and poly(ethylenimine) sorbents, offering important insights that could enhance the efficiency and durability of DAC systems.
"This study underscores the importance of considering all atmospheric components in the design of DAC processes and materials," said Simon Pang, corresponding author and principal investigator of the project. "Our findings will be instrumental in developing next-generation sorbents with enhanced durability, contributing to more efficient and cost-effective carbon-capture solutions."
Amine-based sorbents are at the forefront of DAC technology due to their exceptional ability to efficiently capture CO2 even at ultra-dilute conditions. However, the long-term stability of these materials has been a significant challenge, primarily due to oxidative degradation. The research team investigated the previously unresolved role of CO2 in the oxidative degradation process of these sorbents, reconciling conflicting data in existing literature. The study reveals that CO2 exerts a non-monotonic effect on the oxidation kinetics of poly(ethylenimine) sorbents, with its impact varying significantly depending on temperature and CO2 concentration.
"Our research highlights the dual role of CO2 in the oxidation process," said Sichi Li, lead author of the paper and co-investigator of the project. "On one hand, CO2 catalyzes critical oxidation reactions, while on the other, it reduces polymer branch mobility, which slows down radical propagation. These contrasting effects are key to understanding the complex degradation profiles we observed."
The study's conclusions extend beyond reconciling existing literature, offering practical implications for the future of DAC technology. By identifying polymer side chain mobility and the presence of acidic environments as major factors accelerating oxidation, the research suggests new strategies to enhance sorbent longevity. Potential solutions include the introduction of functional groups, additives or oxide supports with surface chemistry designed to reduce polymer mobility or neutralize acidic conditions, thereby mitigating the rate of oxidative degradation.
LLNL co-authors also include Marcos F Calegari Andrade, Elwin Hunter-Sellars, Amitesh Maiti and Anthony J. Varni. The research is funded by the Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. Computing resources were provided by the LLNL Grand Challenge Program.
