First-principles modeling of H2CO3 molecular adsorption on CaSiO3(001) surface for application in the sequestration and utilization of CO2

Abstract

This work employed density functional theory (DFT) to further study the adsorption of H₂CO₃, HCO₃⁻, and CO₃²⁻ 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 CO₃²⁻ 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 CO₃²⁻. The other adsorption models of HCO₃⁻ and all the adsorption models of CO₃²⁻ have positive adsorption energies. Considering the adsorption process of H₂CO₃, HCO₃⁻ and CO₃²⁻ adsorption reactions may occur successively to some extent depending on the environment.