A theory of the electrical double layer and the interpretation of differential capacity curves

1954 ◽  
Vol 50 ◽  
pp. 373 ◽  
Author(s):  
M. A. V. Devanathan
Keyword(s):  
Double Layer ◽  
Electrical Double Layer ◽  
Differential Capacity ◽  
Capacity Curves

The structure of the electrical double layer in the presence of adsorbed organic molecules

1961 ◽  
Vol 264 (1316) ◽  
pp. 133-144 ◽  
Keyword(s):  
Double Layer ◽  
Electrical Double Layer ◽  
Organic Molecules ◽  
Virial Equation ◽  
Differential Capacity ◽  
Free Energy Of Adsorption ◽  
High Coverage ◽  
Virial Equation Of State ◽  
Capacity Data ◽  
Good Agreement

On the model of the electrical double layer previously proposed by the author, equations are derived for the differential capacity of the metal/electrolyte interface in the presence of organic molecules. It is shown that the equations apply even when ions are specifically adsorbed. A method of calculating the amount of adsorption of the organic species from differential capacity data is outlined and applied to published results for thiourea at the mercury aqueous sodium fluoride interface. It is shown that the results are in good agreement with thermodynamic data. From the calculated adsorption d a ta it is shown that thiourea obeys a virial equation of state but that lateral electrostatic forces are probably negligible except at high coverage. The free energy of adsorption as a function of charge has been evaluated and shown to consist of an electrostatic term and a chemical term which decreases as the electron density of the mercury surface decreases.

The Differential Capacity of the Electrical Double Layer. The Role of the Anion

1952 ◽  
Vol 74 (17) ◽  
pp. 4422-4425 ◽  
Author(s):  
D. C. Grahame ◽  
M. A. Poth ◽  
J. I. Cummings
Keyword(s):  
Double Layer ◽  
Electrical Double Layer ◽  
Differential Capacity

On the specific adsorption of anions in the electrical double layer

1966 ◽  
Vol 290 (1423) ◽  
pp. 527-546 ◽  
Keyword(s):  
Double Layer ◽  
Electrical Double Layer ◽  
Specific Area ◽  
Temperature Sensitive ◽  
Critical Survey ◽  
Covalent Character ◽  
Free Energy Of Adsorption ◽  
Iodide Ions ◽  
Capacity Curves ◽  
Ionic Double Layer

The main experimental facts which should be explained by any ionic isotherm are described. A critical survey of the existing isotherms is made and it is shown that none can explain these facts quantitatively. On the basis of Devanathan’s model of the electrical double layer, an isotherm is derived which satisfactorily explains quantitatively all the facts cited. It is further shown that in this isotherm all the parameters except that involving the noncoulombic part of the free energy of adsorption can be predicted from theory. An evaluation of this non-coulombic energy is made for chloride, bromide and iodide ions from the thermodynamic data of Devanathan & Peries. It is shown that it is independent of the charge of the interface and that it increases linearly with the percentage covalent character of the mercuryhalide bond. With the aid of the isotherm, the broad features of the differential capacity curves are interpreted, in particular the nature of the hump is explained. Pronounced humps are attributed to the specific area of the molecule which may be due to its molecular structure or due to its hydration structure. The latter type of humps called 'hydration humps’ which are observed with ions like nitrate or perchlorate should be temperature sensitive, whereas the former ones should be independent of temperature. It is shown that the inner layer parameters used by Devanathan have been independently confirmed, with the isotherm providing confirmation of K 1-2 . The present status of the ionic double layer is summarized.

Sign in / Sign up

Export Citation Format

Share Document