Silver electrodes charge density

While in the mentioned work on PABA on a charged silver electrode also the adsorption degree of the molecules was controlled by surface charge, Lahann et al. showed a concept in which molecules immobilized as a low-density self-assembled monolayer on a gold surface were electrically stimulated to undergo conformational transitions between a hydrophilic and a hydrophobic state (Lahann et al., 2003). Such a surface wetting switch may then be used to immobilize, for example, enzymes, as was discussed in the previous section. This is an example of switching both the orientation and the activity of adsorbed molecules. 

These ideas on the effects of nonuniformity of charge density on the C E) curves were checked years ago for an extreme case— polycrystalline silver in dilute sodium fluoride solutiont (Fig. 23)—in the following way. For a model polycrystalline electrode. 

Recently, Toney et al. [140] published the results of X-ray reflectivity measurements on dilute aqueous sodium fluoride solutions near positively and negatively charged silver electrodes with (111) surface geometry. The analysis shows an oscillatory density profile with three or four density maxima near the interface, qualitatively similar to the results in Fig. 7. They also found a very large shift of the distance of the first... 

Even in dilute electrolyte solutions, many properties of water are strongly modified in the immediate vicinity of a charged interface, especially its density. This effect has chiefly been studied by electrochemists interested in charged metallic surfaces water close to a silver electrode bearing a surface charge of 0.25 Coulomb/m reaches a density of 2.0 i.e., close to that of... 

With the exception of the elegant mononucleation transients on silver deposition at defect-free silver electrodes [115, 156-159], the analysis of the macroscopic current, charge density, and/or capacitance transients does not provide direct access to structural information and molec-ular/atomistic mechanisms of 2D phase formation. Employing dynamic MC simulations of microscopic models, Rikvold and coworkers pointed out that mean-field rate equations, such as the ones based on the Avrami ansatz, are limited especially in the later stage of the overall transition [195]. For systems in which ordered phases are involved, the microscopic adlayer structure and the dynamic details of the adsorption, phase formation, and lateral diffusion processes should become important [196-198]. The combination of time-resolved dynamical MC simulations... 

FIG. 8. Frequency shift versus surface charge density on gold and silver electrodes in 0.1 M solution of LiC104 in water (a) and in butanol (b). (Fig. 8a from Ref 98.)... 

Summary. We present a brief survey of methods that utilize computer simulations and quantum and statistical mechanics in the analysis of electrochemical systems. The methods, molecular dynamics and Monte Carlo simulations and quantum-mechanical density-functional theory, are illustrated with examples from simulations of lithium-battery charging and electrochemical adsorption of bromine on single-crystal silver electrodes. 

If the areas of the electrodes are assumed to be 1 cm, and taking the equilibrium exchange current density /g for the Ag /Ag equilibrium to be 10 A cm", then /g will be 10 A, which is a very high rate of charge transfer. A similar situation will prevail at electrode II, and rates of exchange of silver ions and the potential will be the same as for electrode I. 

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