Structural and electronic properties of graphene and its derivatives physisorbed by ionic liquids

The interaction between ionic liquids (ILs) with 2D surface of graphene and its derivatives is significant in developing the better energy storage devices. Herein, the interaction of ILs such as [Emim](+)[X](-)- and [Bmim] [X](-) (X = AlCl4, BF4, Cl and PF6) on graphene, crown ether graphene, graphenylene and graphyne surfaces are investigated using Density Functional Theory (DFT). We found that the physisorption of ILs on the 2D surface is mainly by the imidazolium ring and methyl group of cations driven by the van der Waals interaction. The ILs containing BF4- - anion exhibit strong interaction with the considered 2D surfaces and the adsorption does not depend on the chain length of cations. The strong adsorption of ILs on the crown ether graphene sheet reveals the extent of influence of reactive element along with its distinct pore radius on adsorption of ILs compared to the adsorption of ILs on other graphene surfaces. The interaction between cations and BF4 anion forming C-H center dot center dot center dot F bond is undisturbed even on interaction with the 2D surfaces. The minimal change in the anion-cation interaction with the 2D surface strengthens the adsorption. The charge transfer from ILs to 2D surface is found from NPA charge analysis and the bond strength between ILs-2D complexes were identified from topological analysis. The desorption of ILs is inferred from the thermochemical parameters of complexes.