Revealing the different performance of Li(4)SiO(4) and Ca(2)SiO(4) for CO(2) adsorption by density functional theory

To reveal the difference between Li(4)SiO(4) and Ca(2)SiO(4) in CO(2) adsorption performance, the CO(2) adsorption on Li(4)SiO(4) (010) and Ca(2)SiO(4) (100) surfaces was investigated using density functional theory (DFT) calculations. The results indicate that the bent configuration of the adsorbed CO(2) molecule parallel to the surface is the most thermodynamically favorable for both Li(4)SiO(4) and Ca(2)SiO(4) surfaces. The Li(4)SiO(4) (010) surface has greater CO(2) adsorption energy (E(ads) = −2.97 eV) than the Ca(2)SiO(4) (100) surface (E(ads) = −0.31 eV). A stronger covalent bond between the C atom of adsorbed CO(2) and an O(S) atom on the Li(4)SiO(4) (010) surface is formed, accompanied by more charge transfer from the surface to CO(2). Moreover, the Mulliken charge of O(S) atoms on the Li(4)SiO(4) (010) surface is more negative, and its p-band center is closer to the E(f), indicating O(S) atoms on Li(4)SiO(4) (010) are more active and prone to suffering electrophilic attack compared with the Ca(2)SiO(4) (100) surface.