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 (CO32-), 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.