Region of zero charging

Unknown phenomenon was observed on the oxidized surface of a number of metals in water solutions including nickel, palladium, and platinum. Elastic extension of the metal decreases the interface capacity in wide potential region which reaches 0.4 V in the case of palladium. Within such region, the oscillograms “estance vs. potential” disclose an unusually long and low flat section which may be considered as the expanded zero of the differential charge density. The decrease of the capacity points out strengthening the bond of the water molecules to the surface oxide under its elastic extension which thickens the hydrated envelops of the adsorbed ions. Along the flat section, the state of the interface is reversible without changing the structure of the surface oxide. The anodic boundary of the flat section can be used as a sign of reaching the oxide monolayer. In the equations of solid state electrocapillarity, the potential of zero charge is presented explicitly. Its derivative with respect to elastic deformation is independent of the electrode potential and shifts the reversible section of the estance curve along the ordinate.