Classical Density Functional Study on Interfacial Structure and Differential Capacitance of Ionic Liquids near Charged Surfaces

We designed a coarse-grained model for aromatic ionic liquids [CnMIM [Tf2N −] with cations containing different alkyl groups. Within the framework of correlation-corrected density functional theory, the interfacial structure of studied ionic liquids are compared over a range of surface charge densities, alkyl chain lengths and surface geometries. The nonpolar hydrocarbon chains on cation tend to stretch out on the neutral surface. Differential capacitance of electric double layer formed by ionic liquids is explored with respect to surface electric potential. Comparison of ionic liquids model adjacent to planar, cylindrical and spherical surfaces confirms that higher and flatter differential capacitance curve is attributed to larger curvature of the surface. The influence of lengthening cation’s alkyl chain on electrochemical properties is examined as well.