Revealing the different performance of Li4SiO4 and Ca2SiO4 for CO2 adsorption by density functional theory

To reveal the difference between Li4SiO4 and Ca2SiO4 in CO2 adsorption performance, the CO2 adsorption on Li4SiO4 (010) and Ca2SiO4 (100) surfaces was investigated using density functional theory (DFT) calculations. The results indicate that the bent configuration of the adsorbed CO2 molecule parallel to the surface is the most thermodynamically favorable for both Li4SiO4 and Ca2SiO4 surfaces. The Li4SiO4 (010) surface has greater CO2 adsorption energy (Eads = -2.97 eV) than the Ca2SiO4 (100) surface (Eads = -0.31 eV). A stronger covalent bond between the C atom of adsorbed CO2 and an OS atom on the Li4SiO4 (010) surface is formed, accompanied by more charge transfer from the surface to CO2. Moreover, the Mulliken charge of OS atoms on the Li4SiO4 (010) surface is more negative, and its p-band center is closer to the Ef, indicating OS atoms on Li4SiO4 (010) are more active and prone to suffering electrophilic attack compared with the Ca2SiO4 (100) surface.