(227c) Effect of Pore Size, Pore Geometry and Pore Loading On the Properties of Ionic Liquids Confined Inside Nanoporous Carbons

Ionic liquids (ILs) have potential applications as alternative electrolytes in devices such as electrochemical double layer capacitors and dye-sensitized solar cells. In these devices, the electrodes typically consist of a nanoporous material which is in contact with the IL. However, a fundamental understanding of the behavior of ILs inside nm-sized pores is still lacking. Such knowledge is essential to optimize the performance of these IL-based devices. In this study we investigate the behavior of 1,3-dimethylimidazolium chloride, [Dmim][Cl], confined inside two model carbon pores: (1) a slit-like graphitic pore model, and (2) a model CMK-3 material, which consists of amorphous carbon rods arranged in a hexagonal array. We report molecular dynamics results that aim at understanding the influence of (1) pore geometry and size, and (2) pore loading, on the structural and dynamical properties of the confined IL. We observe layering of the ions in both pore geometries, with the number of layers depending on pore size, pore geometry and density of the confined IL. It is also found that increasing the pore loading leads to an important slow-down in the dynamics, especially when the density of the confined IL is larger than the bulk density at room temperature. The effect of pore size, geometry and loading on the radial distribution functions, density profiles, orientation of the ions and dynamics of the ions is also evaluated and discussed, as these molecular-level properties impact the macroscopic properties (e.g., electrical capacitance and resistance) of these systems.