Surface complexation models electrolyte-binding constants

The site binding model based on reactions (1), (2), (14) and (15), often called surface complexation model (SCM), was, beside the simple site binding models (for example two layer model or constant capacitance model) readily applied to a description of the edl on the metal oxide-electrolyte solution interface. Reactions (14) and (15) describe the adsorption of so-called back-... 

Model h is the so-called four layer model, which, compared to the triple-layer model, introduces one supplementary layer. The major reason for this is that the electrolyte ions typically differ in size. It may be argued that the usually larger anion has to be placed further away from the surface than the more compact cation. The consequence of the additional layer is an additional capacitance value. Furthermore, constraints on electrolyte binding from experimental data, which indicate symmetrical electrolyte binding, become more complicated. This is because in addition to the stability constant for the formation of the outer-sphere complexes, the location of charge also affects the interaction of the ion with the surface. 

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