Adsorption behavior of carbonic acid on gamma-dicalcium silicate surface from molecular simulations

This paper aims to investigate the adsorption of carbonic acid and water molecules on the (010) surface of gamma-dicalcium silicate (gamma-C2S) at an atomic scale using density functional theory (DFT) and ab initio molecular dynamics. It provides novel insights into the mechanism of carbonation on the surface of gamma-C2S. The electrons transfer and interfacial reactions between the carbonic acid (H2CO3) molecule and the gamma-C2S surface are characterized by adsorption configuration, bond order, electron density difference, and partial density of states. There exist strong interactions between H2CO3 and gamma-C2S surface, including two types of chemical adsorption and one type of physical adsorption. This work confirms that water in the carbonation of gamma-C2S is to react with CO2 to provide the reactants, and protons transfer of the carbonic acid molecule plays a crucial role in the carbonation process. The adsorption of the carbonic acid molecule is more favorable with respect to that of the water molecule, which may be the initial step of the carbonization of gamma-C2S.