Ion Solvation and Transport in Narrow Carbon Nanotubes: Effects of Polarizability, Cation-p Interaction and Confinement

Understanding ion solvation and transport under nanoscale confinement is important for a wide range of emerging technologies such as energy storage and water desalination. While molecular dynamics simulations have been commonly used to study the behaviors of ions under confinements, there are still considerable deviations between the simulation results depending on the specific treatment of intermolecular interactions. In this work, we present a systematic investigation of structure and transport properties of aqueous salt solutions (KCl and LiCl) confined in narrow carbon nanotubes by using a combination of first-principles and classical molecular dynamics simulations with and without the inclusion of polarization effects. The inclusion of both polarization and cation-p interactions are found to be essential for the description of ion solvation under confinement. In addition, our simulations point to a strong correlation between ion dehydration and diffusion, particularly for KCl, which shows the important role of cation-p interactions in the transport properties of ions in these narrow CNTs. Thus, our study shows that the ion solvation and transport properties are strongly influenced by the complex interplay between nanoconfinement and specific intermolecular interactions.