Hydrogen inner Helmholtz, layer

The solvent molecules form an oriented parallel, producing an electric potential that is added to the surface potential. This layer of solvent molecules can be protruded by the specifically adsorbed ions, or inner-sphere complexed ions. In this model, the solvent molecules together with the specifically adsorbed, inner-sphere complexed ions form the inner Helmholtz layer. Some authors divide the inner Helmholtz layer into two additional layers. For example, Grahame (1950) and Conway et al. (1951) assume that the relative permittivity of water varies along the double layer. In addition, the Stern variable surface charge-variable surface potential model (Bowden et al. 1977, 1980 Barrow et al. 1980, 1981) states that hydrogen and hydroxide ions, specifically adsorbed and inner-sphere... 

A more sophisticated model is the triple-layer model, allowing the surface reaction of the background electrolyte (Hayes et al. 1991). The potential-determining ions (hydrogen and hydroxide) are directly on the surface (inner Helmholtz layer), the other ions are at a certain distance from the surface (outer Helmholtz layer), and there is a diffuse layer, also. 

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