First-principles modeling of H₂CO₃ molecular adsorption on CaSiO₃(001) surface for application in the sequestration...

This work employed density functional theory (DFT) to further study the adsorption of H₂CO₃, HCO₃^-, and CO₃^2- on the CaSiO₃(001) surface, which could provide additional insights into the mechanism of carbonation on the CaSiO₃ surface. It was concluded that the carbonation of CO₂ promoted carbon sequestration, whereby the aqueous carbonation route increased the reaction rate substantially compared to direct gas-solid carbonation. H₂CO₃ is more conducive to CO₂ sequestration, which can be attributed to the interaction of H atoms with the surface. Further, H₂CO₃ can be converted into HCO₃^- or CO₃^2- on the CaO-terminated (001) surface, whereas only HCO₃^- was formed on the SiO-terminated (001) surface. All the adsorption energies of H₂CO₃ were negative, suggesting that H₂CO₃ adsorption was energetically stable and spontaneous. The most likely adsorption model of HCO₃^-, having negative adsorption energy, was the one adsorbed on the SiO-terminated (001) surface, in which HCO₃^- is transformed into CO₃^2-. The other adsorption models of HCO₃^- and all the adsorption models of CO₃^2- have positive adsorption energies. Considering the adsorption process of H₂CO₃, HCO₃^- and CO₃^2- adsorption reactions may occur successively to some extent depending on the environment.