Nano-confined ionic liquid [emim][PF6] between graphite sheets: A molecular dynamics study

We have presented molecular dynamics (MD) simulations on the IL [emim][PF6] confined between the graphite sheets with the different distances of 1, 2, 3, 4, and 5 nm. The vertical and longitudinal pressures and compressibility factors have been calculated and two separate equations of state for the vertical and longitudinal directions for the confined system have been derived by considering the anisotropic pressure tensor. We have also investigated the effects of pore size and pore loading on the structural and dynamical properties of the confined ions. Our structural results showed a significant layering at the IL-graphite interface which indicates strong interaction between the IL and the graphite sheets. Our radial distribution function (RDF) results showed that the cation anion RDF is greater than the other RDFs, indicating a strong interaction between cations and anions which is responsible for the H-bond formation. The average number of the hydrogen bonds also increased as the pore size decreased. The average number of the H-bonds also increases as the pore loading increases. Our dynamical results showed that the self diffusion coefficient of both cations and anions increases with increase in pore size. Also, the self diffusion of the confined ions decreases with increasing the pore loading. (C) 2016 Elsevier B.V. All rights reserved.