(253i) A Grand Canonical Monte Carlo Simulation-Based Method for the Calculation of Electrical Potential inside Nano-Porous Electrodes

Excess charge at the surface of an electrode, created via an externally applied potential, results in an accumulation of counterions near the surface and a depletion of coions in that region. Therefore, it creates an excess electric potential at the interface. This potential drops as the distance from the surface to the Galvani potential in the solution bulk. This phenomenon is known as the electrical double layer (EDL). The EDL governs natural phenomena like colloidal stability and electrokinetic phenomena; and affects the outcome of electrochemical reactions. Classical Theory describes the EDL via the combination of the Poisson equation for electrical potential and the Boltzmann distribution of charge within an electric field next to a planar charged solid surface. This approach treats ions as non-interacting point charges in the vicinity of a single-charged surface in contact with a bulk solution. However, most current applications where EDL is relevant involve confinement within nanostructures, where the size of the ions is within one or two orders of magnitude of the size of the structure itself.

We will present a method to describe the EDL within charged slit-type nanopores that combines Grand Canonical Monte Carlo simulations (GCMC) with electrodynamics concepts to determine not only the EDL structure, but most importantly the profiles of electrical potential. The method was validated against the simplest case where Classical EDL Theory can be applied (two parallel planar surfaces with no EDL overlap) and then extended to increasingly confined spaces. In contrast to classical EDL theory, this method accounts for ion-size and ion-ion interactions; and provides insights into the EDL properties within nanostructures.