NaCl Ion Pairing at Liquid-Insulator and Liquid-Conductor Interfaces

Abstract

We study the formation and dissociation of NaCl ion pairs at water-insulator and water-conductor interfaces, a crucial process in determining the structure and composition of interfacial electrolytes. Using Molecular Dynamics simulations, we show that both ions remain strongly hydrated and excluded from the interfacial region, where water layering is significant. This enables a successful treatment of ion pairing at the water-insulator interface with a simple dielectric continuum theory with no free parameters. However, in contradiction to this simple theory, the water-electrode interface acts as a water-insulator interface from the perspective of the NaCl ion pairing we consider here.