Density functional theory study of adsorption of ionic liquids on graphene oxide surface

Abstract

Understanding the interaction between ionic liquids (ILs) and graphene oxide (GO) is essential for the wide application of IL–GO systems. In this study, the microstructure formed by ILs ([Bmim][BF4], [Bmim][B(CN)4], [Bmim][PF6] [Bmim][TF2N]) on the surface of GO and the interaction between these species were investigated using density functional theory. The orbital energy, charge transfer, and influence of adsorption on the hydrogen bonds between the cations and anions were considered. Calculations of the orbital energy and density of states indicate that the HOMO-LUMO energy gap of the ILs is reduced after adsorption on the surface of GO. Atoms in molecules (AIM) analysis showed that the hydrogen bonding interaction between the cations and anions of the ILs decreased when the ILs were adsorbed on GO. Charge transfer between the ILs and GO plays an important role in adsorption of the ILs on GO. When the ILs were on the hydroxyl side of the GO surface, the main operative forces were hydrogen bonds and van der Waals interactions. However, when the ILs were not on the hydroxyl side of the GO surface, weak van der Waals interactions between the ILs and GO played a key role, mainly via X⋯π, CH⋯π, and π⋯π interactions.