XXXVI Reunión Bienal de la Real Sociedad Española de Física

Computational study of mixtures of ILs and alcohols under nanoconfinement conditions

19 Jul 2017, 18:40

20m

Aula Matemáticas (Facultad de Química (USC))

Oral parallel contribution Molecular Physics at the Edge Molecular Physics at the Edge II

Description

Mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] ionic liquid with molecular amphiphilic solvents, methanol and ethanol under nanoconfinement between neutral and charged graphene walls are studied in this work by means of molecular dynamics simulations. The adsorption of alcohol molecules in the walls as well as their distribution in the directions normal and parallel to the interface are studied. The results of these simulations are compared with results of the pure IL and its mixtures with water, which were previously reported in ref. [1]. All the results suggest that alcohols distribute quite uniformly throughout the box, being almost totally depleted from graphene walls. The distribution of ions of the first and second layers closest to the electrodes in the direction parallel to these are also studied by means of bidimensional density maps, showing a clear structural transition from a striped pattern to an hexagonal one with the concentration of cosolvent and also when the size of the cosolvent molecules increases. These transitions seem to be highly sensitive to the presence of cosolvent molecules in the ionic layers closest to the electrodes. It was also corroborated that the bidimensional ionic structures persist in the second ionic layer close to the graphene walls. This persistence of the bidimensional ionic structure combined with the electric double layer (see refs. [2-5]) strongly conditions the three dimensional ionic structure near charged interfaces in these dense ionic systems. Moreover, recent studies have shown that this bidimensional structures appear in ILs in other circumstances, like mixtures with salts, mixtures with other cosolvents solvents like water or when the graphene walls have vacancy defects (see ref. [6]). In this work we report the formation of these structures when the molecular size of the solvent changes. References [1] B. Docampo-Álvarez, V. Gómez-González, H. Montes-Campos, J. M. Otero-Mato, T. Méndez-Morales, O. Cabeza, & L. M. Varela (2016). J. Phys. Cond. Mat., 28(46), 464001. [2] A. A. Kornyshev, (2007). J. Phys. Chem. B, 111(20), 5545-5557. [3] M. V. Fedorov & A. A. Kornyshev, (2008). J. Phys. Chem. B, 112(38), 11868-11872. [4] M. V. Fedorov, N. Georgi & A. A. Kornyshev, (2010). Electrochem. Commun., 12(2), 296-299. [5] M. Z. Bazant, B. D. Storey & A. A. Kornyshev, (2011). Phys. Rev. Lett., 106(4), 046102(1)-046102(4). [6] H. Montes-Campos, J. M. Otero-Mato, T. Méndez-Morales, O. Cabeza, L. J. Gallego, A. Ciach, R. M. Lynden-Bell & L. M. Varela, (2017). Submitted for publication.