Molecular structure and transport of ionic liquid confined in asymmetric graphene-coated silica nanochannel

Abstract The transport of ionic liquids (ILs) in nanochannel is greatly restricted, and facilitating transport of ILs is of great significance to their applications in gas separation, battery and supercapacitor, etc. In this work, we use molecular dynamic simulation to investigate the molecular structure, charge distribution, diffusion behavior and flow characteristics of [EMIM][BF4] confined in asymmetric graphene-coated silica nanochannel to provide information for guiding the fabricate of nanodevice, and analyze the influence of nanochannel height, coating graphene and driving pressure. Water also studied as a comparison. The results indicate that [EMIM][BF4] and water confined in silica nanochannel present layered structure, and coating graphene on the wall surface of silica nanochannel can enhance the layering effect, and uniformize the charge distribution and reduce the diffusion coefficient. [EMIM][BF4] presents different flow states at varying nanochannel height, including Poiseuille flow and partial plunger flow, but water only presents Poiseuille flow. Coating graphene on wall surface of silica nanochannel results obvious positive slippage on the wall surface and the fast transport in nanochannel.