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

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 compo- sition of interfacial electrolytes. Using Molecular Dynamics simulations, we show that both ions remain strongly hydrated and excluded from the interfacial region where wa- ter 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 param- eters. 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.