Quantum Chemical Simulation for the Adsorption Behavior of Silicon in Water and Surface Property Study

With the rapid development of the photovoltaic industry, the demand for crystalline silicon has significantly increased. Water-based waste slurry generated from silicon wafer cutting with diamond wire is a byproduct, presenting considerable potential for reutilization. However, the presence of moisture can lead to silicon oxidation and SiO₂ layer formation on the surface, hindering the recovery of high-purity silicon. In this study, the first-principles was employed for investigating the adsorption property of H₂O on Si (111) and Si (100) surfaces, based on density functional theory. The results indicate that H₂O can spontaneously adsorb on both the (111) and (100) surfaces of Silicon, and the affinity of H₂O for the Si (111) surface being stronger than the Si (100) surface. Furthermore, Mulliken charge calculations and differential electron density analysis confirm that charge transfer of H, O and Si atoms occurs during the adsorption process between Si and H₂O. The Si–O bonds formed on the Si (111) surface exhibit greater covalency compared to the Si (100) surface, suggesting that the Si (111) face is more susceptible to oxidation than the Si (100) face. This study provided theoretical insight into the adsorption of silicon in water at the atomic level, which is significant for deepening the understanding of silicon's oxidation mechanisms.