Steric effects on ion dynamics near charged electrodes

Abstract

We present a modified Poisson–Nernst–Planck (mPNP) model to include steric effects on ion dynamics near charged electrodes. This contribution appears directly on chemical potential of each ion in solution as a non-electrostatic term. The model consists in a partial-differential-algebraic equation (PDAE) system, which after spatial discretization was solved by the well-established DASSLC code, implemented in EMSO simulator. A careful dimensional analysis was carried out to turn the PDAE system dimensionless with normalized spatial domain. Size correlation (SC) effects for equally sized ions avoid unphysical charge densities near the electrodes (especially at high voltages), and also give some insights on double layer formation. Time evolution of free charge density profiles show a diffusion controlled dynamics with a very fast response (t∼10−8s). The methodology proposed here allows the inclusion of new contributions on PNP model framework for ion dynamics, as well as to solve both stationary and dynamical ion distributions, taking advantage of the EMSO software simulator features.