Molecular dynamics simulations of CO2 at an ionic liquid interface: adsorption, ordering, and interfacial crossing

Area of Science:

• Physical Chemistry
• Chemical Engineering

Background:

• Ionic liquids (ILs) are investigated for carbon dioxide (CO2) capture applications.
• Understanding the behavior of IL-CO2 systems at interfaces is crucial for efficient capture technologies.

Purpose of the Study:

• To investigate the interfacial properties and dynamics of the ionic liquid 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]) in contact with CO2.
• To characterize CO2 adsorption, diffusion, and desorption at the IL-gas interface using molecular dynamics.

Main Methods:

• Classical molecular dynamics simulations were employed.
• Simulations were conducted at various temperatures and pressures for both vacuum-liquid and CO2-liquid interfaces.
• Interfacial ordering, CO2 adsorption/desorption dynamics, and transport properties (fluxes, diffusivities) were analyzed.

Main Results:

• The interfacial structure of [bmim][Tf2N] remained largely unchanged upon contact with CO2.
• CO2 rapidly adsorbed to form a dense interfacial layer, with subsequent diffusion into the bulk occurring slowly.
• A distinct dense CO2 layer was observed during desorption into CO2, unlike desorption into a vacuum.

Conclusions:

• The study provides insights into the interfacial behavior and transport dynamics of IL-CO2 systems.
• The findings support the potential of ionic liquids for CO2 capture, highlighting the rapid interfacial CO2 accumulation.
• Further characterization of interfacial phenomena is essential for optimizing CO2 capture processes using ionic liquids.