(507b) The Effect Of Confinement On The Structural And Transport Properties Of Model Ionic Liquids

The unique properties of ionic liquids (ILs) made them very attractive for several applications. In particular, in the last few years, ILs have been proposed as alternative electrolytes for dye-sensitized solar cells with nanocrystalline semiconductors [1], electrochemical sensors employing carbon composite materials [2], and activated carbon or carbon nanotube ? based supercapacitors [3]. In all these applications the liquid-solid interfacial properties play a major role. As a result of finite size effects and adsorptive forces, the ionic liquids confined in a nanoporous structure display a different behaviour with respect to the bulk [4]. The structural charge arrangement and ionic mobility inside the pores are determinant for the electrochemical performance of all these devices based on IL-embedded porous materials.

The overall objective of our work is to advance in the understanding of the different microscopic effects leading the macroscopic behavior of ILs in confined environments. As a first step in this long term project, we have concentrated in model ILs and model porous materials, and studied its microscopic-macroscopic behaviour by using molecular simulation tools. We will first present and discuss the results of a series of molecular-dynamics simulations of 1-ethyl,3-methylimidazolium chloride confined in graphite slit-like nanopores. For this particular system we investigate the structure and dynamics of the liquid layer as a function of the separation between carbon walls, concentrating on the molecular and charge density profiles, radial distribution functions, diffusion coefficient and angular orientations near the carbon plates. Later stages of this work include the influence of the alkyl-chain length on the adsorption process as well as the influence of charges distributed along the adsorbing plates. Our final goal is to model the best ILs/surface combination for specific applications.

This work is partially financed by the Spanish Government under project CTQ2005-00296/PPQ and by Generalitat de Catalunya (2005SGR-00288)

[1] C. Pinilla, M.G. Del Popolo, R.M. Lynden-Bell, J. Kohanoff, J. Phys. Chem. B (2005), 109, 17922. [2] F. Zhao, X. Wu, M.K. Wang, et al. Anal. Chem. (2004), 76 (17): 4960-4967 . [3] T. Sato, G. Masuda, K. Takagi, Electrochim. Acta. (2004), 49 (21): 3603-3611 . [4] C. Rey-Castro, L.F. Vega, J. Phys. Chem. B (2006), 110 (29): 14426-14435.