Classical molecular dynamics simulations with polarizable potential models
were carried out to quantitatively determine the effects of KCl salt concentrations on the
electrostatic surface potentials of the vapor-liquid interface of water. To the best of our
knowledge, the present work is the first calculation of the aqueous electrolyte surface
potentials. Results showed that increased salt concentration enhanced the electrostatic
surface potentials, in agreement with the corresponding experimental measurements.
Furthermore, the decomposition of the potential drop into contributions due to static
charges and induced dipoles showed a very strong effect (an increase of ~1V per 1M)
due to the double layers formed by KCl. However, this was mostly negated by the
negative contribution from induced dipoles, resulting in a relatively small overall
increase (~0.05V per 1M) with increased salt concentration.