Modeling CO2 Transport and Sorption in Carbon Slit Pores

The need to reduce carbon dioxide (CO2) emissions is one of the most significant environmental challenges facing society. Carbon capture and storage (CCS) has the potential to mitigate gigatons of anthropogenic CO2 emissions, and is regarded as a key method for global-scale CO2 emissions reduction. Understanding CO2 adsorption and transport is crucial to the development of successful carbon capture and storage technologies. This work investigates the use of an improved potential model to directly treat CO2 electrostatic and geometric properties, thereby more accurately describing the fluid–fluid and fluid–wall interactions that determine adsorption capacity and dynamics. Nonequilibrium molecular dynamics (NEMD) simulations are conducted to investigate pore entrance effects on transport through carbon pores. CO2 interactions with pure and hydroxyl-functionalized slit and step carbon pores are simulated to investigate pore entrance effects and trade-offs among pore size, chemistry, capacity, and transport. The relative importance of (1) CO2 geometry and flexibility, (2) electrostatic interactions, and (3) pore surface chemistry is investigated. The transport investigations of CO2 through carbon pores suggest that fluid density, diffusivity, and permeability are sensitive to the potential model used to describe molecular interactions, pore size, pore geometry, and surface chemistry. The differences in capacity and dynamic properties between the step and slit cases show the importance of investigating transport using models that account for different types of mass transfer resistance. The current work highlights the importance of the potential and structure models in molecular simulations of adsorption and dynamics. These fundamental studies indicate the significance of molecular-scale phenomena for carbon dioxide transport in the confined spaces for CCS applications.