Electrochemistry boundary between different phases

At any given interface between two phases the properties of both phases close to the interface and, in particular, those of the topmost layers are different from those in the bulk. In order to separate this special portion of a system from both bulk phases the term interphase has been coined for this quasi-phase in between the bulk phases. This term considerably expands the two-dimensional view of the phase boundary as a simple interface between two completely homogenous phases. The particular properties of these interphases are of pivotal importance for their behavior in many areas of science and technology. In applied sciences an improvement of these properties is possible only with knowledge of these properties that is as broad and deep as possible. In electrochemistry the interphase properties are further complicated by the involvement of charged particles and extremely high electric fields. A broader overview of the electrochemical interface will identify further adjacent domains ... 

When charges are separated, a potential difference develops across the interface. The electrical forces that operate between the metal and the solution constitute the electrical field across the electrode/electrolyte phase boundary. It will be seen that although the potential differences across the interface are not large ( 1 V), the dimensions of the interphase region are very small (—0.1) and thus the field strength (gradient of potential) is enormous—it is on the order of 10 V cm. The effect of this enormous field at the electrode/electrolyte interface is, in a sense, the essence of electrochemistry. 

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