Study on the Microscopic Mechanism of Adsorption and Diffusion Behavior of CO₂ Storage in the Cap Bed

To address the critical issues related to carbon dioxide (CO₂) geological sequestration in the context of greenhouse gas mitigation, The adsorption and diffusion behaviors of CO₂ within SiO₂ slits were investigated using molecular simulation techniques, including grand canonical Monte Carlo simulations, molecular dynamics simulations, and density functional theory. The findings reveal that the adsorption of CO₂ intensifies with increasing pressure and decreasing temperature. Additionally, hydrophilic SiO₂ slits exhibit a higher CO₂ adsorption capacity compared to hydrophobic SiO₂ slits. Moreover, as the width of SiO₂ slits increases, both the adsorption and diffusion capabilities of CO₂ gradually enhanced. Furthermore, the adsorption energy, adsorption height, and charge transfer were conducted to elucidate the microscopic mechanisms governing CO₂ adsorption on SiO₂ surfaces with varying wettability. The results provide molecular-level insights into the interaction mechanisms between CO₂ molecules and SiO₂ nano confinement surfaces with different rock properties. The result contributes valuable theoretical guidance for understanding the adsorption mechanisms of CO₂ in caprock formations and its long-term sequestration in geological reservoirs.