Stern-Gouy-Chapman model

This Gouy-Chapman-Stern model, as it was named after its main contributors, is a highly simplified model of the interface, too simple for quantitative purposes. It has been superseded by more realistic models, which account for the electronic structure of the metal, and the existence of an extended boundary layer in the solution. It is, however, still used even in current publications, and therefore every electrochemist should be familiar with it. 

Figure 17.1 The Gouy-Chapman-Stern model, the solution. We will consider each phase in turn.

Eq. (6) represents the Stern portion of the Gouy-Chapman-Stern model. Stern reactions are strong interactions, represented as binding in Eqs. (1) and (2), between ions and the PM that alter cr. These associations are different from charge screening (described next), which does not eliminate surface charge but merely reduces the negativity of the potential. 

Table 1 presents parameter values for the Gouy-Chapman-Stern model. The experimental methods for their determination will be described later. 

Fig. 4. A comparison of studies in which 1/Ap and y/cw were measured and computed. For (A), parameters for a Gouy-Chapman-Stern model were evaluated for eight studies for (B), parameters for a Donnan-plus-binding model were evaluated for five studies. Optimized values for total negative sites (Rj) were computed for each study, but a single suite of binding constants was evaluated for the pooled PM data and for the pooled CW data. The figure is redrawn from Shomer et al. (2003).

We are confident that a Gouy-Chapman-Stern model and a Doiman-plus-binding model may be used to compute values for xj/p and y/cyf that are at least proportional to the actual values. With these electrical potentials, corresponding values for ion activities may be computed that are at least proportional to actual values also. Although the electrostatic theory is quite old, values for model parameters for plant cell surfaces have become available only recently. Computer programs for the electrostatic models may be requested from us. 

Kinraide, T.B., 1994. Use of a Gouy-Chapman-Stern model for membrane-surface electrical potential to interpret some features of mineral rhizotoxicity. Plant Physiol. 106, 1583-1592. 

K.B. Oldham, A Gouy-Chapman-Stern model of the double layer at a metal ionic liquid interface,... 

The diffuse double layer model of Gouy and Chapman works reasonably well for systems of relatively low surface potential (electrolyte concentration (< 10 M). At higher surface potential and ionic strength the outer part of the double layer may still obey this model, but the inner part close to the surface tends toward the molecular condenser. Therefore, these two pictures are integrated in the Gouy-Chapman-Stern model. 

The Gouy-Chapman-Stern model of the electrical double layer may be understood as two condensers in series, so that for the total capacitance C, ... 

Rytwo, G. 2004. Applying a Gouy-Chapman-Stern model for adsorption of organic cations to soils. Applied Clay Science 24, no. 3 137-147. doi 10.1016/j.clay.2003.01.001. 

Zeta Potential Measurement, Figure 1 Schematic representation of the electric double layer using Gouy-Chapman-Stern model [3]... 

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