B. B. Damaskinz
Moscow State University, Vorob’evy gory, Moscow, 119991 Russia
Received May 12, 2008
Abstract—The differential capacitance curves are calculated, by using the model of three parallel capacitors,
both for the electrical double layer dense part and the surface layer as a whole, at different ratios of the attraction
constants in this model: a11, a12, and a22. It is shown by regressive analysis of the curves that these capacitance
curves agree well with the model of two parallel capacitors, provided allowance is made for the linear potential
dependence of the effective attraction constant in this model. When allowance is made for the electrical double
layer diffuse part, the agreement with the model of two parallel capacitors is still improved, not only at the
attraction constant critical value a12 = 2 but also at its smaller values (1.5 and 1.0). However, at a12 = 0.5 and
rather high concentration of organic substances whose molecules adsorb in two different orientations the curves
as if get divided into two parts separated with a maximum that reflects the process of the adsorption layer trans-
formation. Under these conditions the model of two parallel capacitors turns to be inapplicable. It follows from
the obtained results that the observed good applicability of the model of two parallel capacitors to the experi-
mental data on the adsorption of numerous aliphatic compounds at electrodes by no means implies that the
adsorption layer structure in the studied systems actually corresponds to the physical picture on which the
model is based.
Key words: adsorption of organic molecules, model of two (three) parallel capacitors, curves of differential
capacitance for the electrical double layer as a whole and its dense part
DOI: 10.1134/S1023193509090134
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