Potential of Zero Charge

a characteristic value of the electrode potential for any metal at which a clean surface of the metal will not acquire an electrical charge when it comes into contact with an electrolyte. The electrolyte, though, must not contain a surfactant.

If the electrode potential is positive in relation to the potential of zero charge, then negative ions are attracted to the metal from the solution; if it is negative in relation to the potential of zero charge, then positive ions are attracted. In both cases, the usual tendency of particles of matter to move from the surface to the bulk phase is repressed; that is, the surface tension at the boundary between the metal and the solution is reduced. With a liquid electrode, for example, a mercury electrode, this effect is easily seen through electrocapillary curves, which show the relationship between the potential of the metal meniscus in contact with the electrolyte and the extent of capillary rise or fall. At the potential of zero charge, the surface tension is at a maximum, and the electrical capacitance at the boundary is at a minimum. The potential of zero charge is important in the study of the kinetics of electrode reactions, in the selection of corrosion inhibitors, and in other cases where it is important to consider the adsorption of components on metal surfaces.