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In this study, the adsorption behaviorof various molecules,includingH2O, CO2, and H2CO3, onthe C2S surface in the carbonation system was systematicallycompared to elucidate the microscopic mechanism in early acceleratedcarbonation using density functional theory and ab initio moleculardynamics. The electronic structures on β-C2S andγ-C2S surfaces differ, in that the valence band maximumis contributed by the O p orbital and Ca s orbital, respectively.This difference results in different proton–surface interactions.The protons hydroxylated the [SiO4]4– tetrahedra on the β-C2S surface. On the γ-C2S surface, the protons enter the interior surface to forma three-coordination configuration with Ca atoms in addition to bondingwith the [SiO4]4– tetrahedra. The adsorptionenergy for the dissociative adsorption of H2CO3 on both β-C2S and γ-C2S surfacesis significantly higher than that of H2O, and the dissociativeadsorption configurations are also more stable. CO2 onlyhas a strong adsorption tendency on the γ-C2S surface,where it acquires electrons from the surface Ca atoms to become activated.In the molecular adsorption phase, γ-C2S interactsmore strongly with CO2, H2CO3, andits dissociation products. Thework is beneficial to deepen the knowledge of the calciumsilicate carbonation mechanism and provide theoretical support forcarbon sequestration.
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