Fixed double layer, model electrochemical interface

This chapter is devoted to the behavior of double layers and inclusion-free membranes. Section II treats two simple models, the elastic dimer and the elastic capacitor. They help to demonstrate the origin of electroelastic instabilities. Section III considers electrochemical interfaces. We discuss theoretical predictions of negative capacitance and how they may be related to reality. For this purpose we introduce three sorts of electrical control and show that this anomaly is most likely to arise in models which assume that the charge density on the electrode is uniform and can be controlled. This real applications only the total charge or the applied voltage can be fixed. We then show that predictions of C < 0 under a-control may indicate that in reality the symmetry breaks. Such interfaces undergo a transition to a nonuniform state the initial uniformity assumption is erroneous. Most... 

This paper attempts to model and define the conditions under which platinum Eh measurements are likely to reflect the true electrical potential of aqueous solutions. The double layer at the surface of the electrode is modeled as a fixed capacitor (C jj), and the rate at which an electrode equilibrates with a solution (i.e. the rate at which C jj is charged) is assumed to be proportional to the electrical current at this interface. The current across the electrode/solution interface can be calculated from classical electrochemical theory, in which the current is linearly proportional to the concentration and electron-transfer rate constant of the aqueous species, and is exponentially proportional to the potential across the interface. 

Figure 2. Three models of the electrochemical interface (a) the Helmholtz fixed (rigid) double layer, 1879 (b) the Gouy-Chapman diffuse double layer 1910-1913 (c)the Stern double layer, 1924, being a combination of the Helmholtz and the Gouy-Chapman concepts.

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See also in sourсe #XX -- [ ]

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