Surface Reaction of CO₂ with Basaltic Minerals as a Mechanism for Carbon Mineralization

Rapid carbon mineralization has been achieved in basaltic rocks; however, the fundamental chemical mechanisms governing the interactions of CO₂-rock remain unclear. Here, ab initio molecular dynamics simulations were performed to elucidate the surface reaction of CO₂ using three basaltic minerals. To mimic natural conditions, the mineral surfaces were first hydrolyzed by water exposure. The simulation provides molecular-scale evidence that naturally occurring basaltic mineral surfaces are CO₂-active. Three previously unrecognized pathways were revealed, distinct from the conventional dissolution-precipitation paradigm. These pathways involve CO₂ directly reacting with hydrolyzed mineral surfaces, at nonbridging oxygens (NBOs) and metal-coordinated hydroxyl groups, forming stable carbonate (CO₃^2-), bicarbonate (HCO₃^-), and hydrogen pyrocarbonate (HC₂O₅^-) species. The surface reaction capacity exhibits a first-order dependence on the density of NBOs. The presence of interfacial water plays a dual role in modulating the CO₂ chemisorption. We find that the surface reaction induces coordination distortion at metal sites, potentially lowering the dissolution energy barrier of carbonated metal ions and facilitating a self-sustaining cycle of surface reactivity renewal. These findings establish the existence of CO₂ surface reactions as a critical yet overlooked driver of enhanced carbon mineralization in basaltic systems.