(166c) Grand Canonical Monte Carlo Simulations of Electrical Double Layer Potential Profiles in Nanopores

Solid surfaces in solution become charged either naturally or via application of an electric field. The excess charge at the surface results in a region in the solution known in electrochemistry as the electrical double layer (EDL). The EDL governs phenomena like colloidal stability and electrokinetic phenomena; it also affects the outcome of electrochemical reactions. Electrical double layers play a key role in applications related to energy storage and water purification. Electrochemical measurements obtain macroscopic properties of EDL such as current response or potential response. Molecular efforts to model EDL usually give electrolyte distribution within the EDL
The work will discuss the utilization of a combination of Grand Canonical Monte Carlo (GCMC) simulations and electrodynamics concepts in order to calculate EDL profiles of electrical potential within charged slit-type pores. Electrical potential distributions inside pores with respect to field-free virtual bulk electrolyte solution implicit in the Grand Canonical ensemble were obtained via this method. The simulations show that entropy effects lead to the exclusion of co-ions from the pore to allow densely-packed counter-ions to efficiently neutralize surface charge. This phenomenon, in conjunction with the long-range effects with respect to the source charge, lead to a semi-oscillatory behavior of the potential profiles not predicted by Classical Theory. The electrical potential at the center of the pore was lower with respect to the absolute potential of the bulk solution in some cases, even if ion-distribution bulk conditions were achieved for a couple of layers of fluid at the center of the pore.