Adsorption of ions and molecules

Although the p.z.c. is difficult to determine experimentally, and although the values obtained vary with the method used, it is of fundamental significance in electrochemistry, since it provides information on adsorption of ions and molecules, i.e. if the potential is negative with respect to the p.z.c. cations will tend to be adsorbed and anions repelled, and vice versa. The p.z.c. appears to be a natural reference point for a rational scale of potentials defined by... 

Capacitance and surface tension measurements have provided a wealth of data about the adsorption of ions and molecules at electrified liquid-liquid interfaces. In order to reach an understanding on the molecular level, suitable microscopic models have had to be considered. Interpretation of the capacitance measurements has been often complicated by various instrumental artifacts. Nevertheless, the results of both experimental approaches represent the reference basis for the application of other techniques of surface analysis. 

Persson, I. Adsorption of Ions and Molecules to Solid Surfaces in Connection with Flotation of Sulfide Minerals. J. Coord. Chem. 1994, 32, 261-342. 

An electrical double layer (edl) existing on the solid-solution interface is essentially connected with the surface properties of the system. The amount of accumulated charge influences the adsorption of ions and molecules. In the latter case it also influences the configuration of the adsorbed species. On the other hand, the adsorption of the ions and molecules varies surface properties of the interface (functional groups) and thus, the distribution of the charge in the interfacial region. The existence of the electric charge at the interface influences the dispersed system stability. 

It is apparent that the adsorption of ions and molecules also affects the cathodic reaction of metallic corrosion. The typical cathodic reaction is the cathodic reduction of hydrated protons and atmospheric oxygen molecules. From the standpoint of corrosion science, however, no systematic studies on this topic seem to have been made in the literature. In practice, the cathodic reaction may occur on the bare metal surface and the surface of metal oxides as well, if present on corroding metals. It is likely that for the cathodic reduction of oxygen molecules and hydrated protons the catalytic activity of the bare surface of metals is greater than that of the surface of metal oxides and... 

Semiconductor corrosion will also be affected by the adsorption of ions and molecules on the semiconductors. We have nevertheless seen in the field of corrosion science almost no reliable research results on the catalytic characteristics of semiconductor corrosion. 

During several decades, the quantitative analysis of the edl structure, adsorption of ions and molecules on the ideally polarizable solid electrodes was carried out on... 

Although many models for the double layer have been published in the literature, there is no general model that can be used in all experimental situations. This is because the double-layer structure and its capacity depend on several parameters such as electrode material (metals, types of carbon, semiconductors, material porosity, the presence of layers of either oxides or polymeric films or other solid materials at the surface), type of solvent, type of supporting eleetrolyte, extent of specific adsorption of ions and molecules, and temperature. 

The adsorption of ions and molecules on the surface of mercury electrodes is a thoroughly investigated phenomenon [51 ]. Surface-active substances are either electroactive [52] or electroinactive [53]. The former can be analyzed by adsorptive stripping voltammetry [54]. This is the common name for several electroanalytical methods based on the adsorptive accumulation of the reactant and the reduction, or oxidation, of the adsorbate by some voltammetric technique, regardless of the mechanisms of the adsorption and the electrode reaction [55, 56]. Frequently, the product of the electrode reaction remains adsorbed to the electrode surface. Hence, the term stripping should not be taken literally in all cases. Besides, some adsorbates may be formed by electrosorption reactions, so that their reduction includes covalently bound mercury atoms. The boundary between adsorption followed by reduction, on the one hand, and electrosorption, on the other, is not strictly defined. Moreover, it is not uncommon that, upon cathodic polarization, the current response is caused by a catalytic evolution of hydrogen, and not by the reduction of the adsorbate itself [57]. However, what is common to all methods is a hnear relationship between the surface concentration of the adsorbate and the concentration of analyte at the electrode surface ... 

The adsorption of ions and molecules on the surface of mercury electrodes is a thoroughly investigated phenomenon [51]. Surface-active substances are either electroactive [52], or electroinactive [53]. The former can be analyzed by adsorptive stripping voltammetry [54]. This is the common name for several elec-troanalytical methods based on the adsorptive accumulation of the reactant and the reduction, or oxidation, of the adsorbate by some voltammetric technique. 

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