Molecular mechanisms of CO2 mineralization on wetting nanoscale surfaces using molecular simulations and metadynamics
Xinping Zhu, Yong Tao, Romain Dupuis, Yining Gao, Chi Sun Poon, Katerina Ioannidou, Roland J.‐M. Pellenq
Abstract
Carbonatable minerals on earth have significant potential to act as gigatonne-scale CO2 sinks. Many carbon removal managements rely on CO2 mineralization on wetting mineral surfaces. Realizing their carbon removal potential requires a fundamental understanding of the atomic-scale mechanisms of mineral carbonation. This study employs reactive/non-reactive molecular simulations and well-tempered metadynamics to elucidate the complete interfacial CO2 mineralization pathways within a portlandite mesopore adsorbed with a nanometric water film. Here we reveal quantitatively, for the first time, a global CO2 mineralization spectrum describing the local molecular environment and the thermodynamics of the five critical steps: water adsorption, calcium dissolution, CO2 adsorption, CO2 speciation, and CaCO3 ion pairing. We identify kinks as the primary reactive sites for surface dissolution and demonstrate how the water film’s acid-base environment modulates these processes, creating an energetically favorable reaction loop for sustained CO2 mineralization. We uncover that quasi-neutral to slightly basic conditions optimize mineralization efficiency by balancing the opposing effects of pH on calcium dissolution and CO2 speciation. Mineral carbonation could enable gigatonne-scale CO2 removal. Here, the authors use molecular simulations to map a full CO2 mineralization pathway at a wetting surface, revealing key reactive sites and optimal pH conditions for efficient carbonation.