8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Tue 611:23-14:00P10.9Electrical response of an electrolytic cell in the presenceof adsorption and recombination of ionsLuiz Evangelista 1 and Ervin Lenzi 11 Universidade Estadual de Maringá, Departamento de Física, Avenida Colombo, 5790,87010340, Maringá, BrazilTo describe the redistribution of ions in a weak electrolyte upon the application of an externalelectric field, usually the fundamental equations to be solved are the continuity equations for thepositive and negative charge carriers and Poisson’s equation for the electric field across the cell.This is the so-called Poisson-Nernst-Planck (PNP) model. To build a more complete model toevaluate the electrical impedance of this system, valid for blocking electrodes, it is also necessaryto take into account the dissociation of neutral particles in ionic products, the recombination ofthese ions giving rise to neutral particles [1, 2], and the adsorption-desorption process occurringat the interfaces. In this paper, we first investigate the importance of the dissociation-associationphenomenon on the electrical impedance of an insulating liquid medium containing ions whenthe adsorption-desorption process is taken into account. Subsequently, the case in which thediffusion coefficients of the positive and neutral particles are zero, a scenario more appropriatedto the description of an insulating gel, is also considered. Finally, the PNP model is consideredin the case in which the mobility of the positive ions is different from that of negative ions, inthe presence of selective adsorption, but neglecting the recombination effects. The problem isanalytically solved and an expression for the electrical impedance of a cell of thickness d isobtained. In this manner, the frequency behavior of the real and imaginary parts of the impedance(admittance) is exactly established.[1] J. Ross Macdonald, Phys. Rev. 92, 4 (1953).[2] G. Derfel, E. K. Lenzi, C. R. Yednak, and G. Barbero, J. Chem. Phys. 132, 224901 (2010).[3] G. Barbero and L. R. Evangelista, Adsorption Phenomena and Anchoring Energy in NematicLiquid Crystals, (Taylor Francis, London, 2006).9