Organic molecules on electrode

Fig. 6.108. Current vs. potential curve for the adsorption of organic molecules on electrodes. The current due to adsorption of organic molecules is a currentless process. When oxidation, reduction, or other electron-transfer reactions take place, high currents may be detected.

Thus, Eq. (6.270) is an isoconc (see Section 6.8.6), which describes the adsorption of organic molecules on electrodes as a substitution process of solvent molecules and takes into account the surface heterogeneity and lateral interactions among the adsorbed species. This isoconc is able to successfully describe and reproduce the parabolic shape—with its maximum in the vicinity of the pzc—of the adsorption process of organic molecules. 

Other Factors Influencing the Adsorption of Organic Molecules on Electrodes... 

The reversible adsorption of organic molecules on electrodes was been discussed in (Section 6.9.3). Here, one is interested in irreversible adsorption, organic molecules that form a film and stick on the electrode through washings and also when the new electrode is used in various reactions. 

A sudden change in coverage, of the type shown in Fig. 171, has been observed in several instances of adsorption of organic molecules on electrodes. It should be understood that such behavior is not necessarily related to charge transfer. The same kind of isotherm can be... 

The measured adsorption effect at the electrode is influenced by all dissolved and/or dispersed surface-active substances according to their concentration in the solution, adsorbability at the electrode, kinetics of adsorption, structure of the adsorbed layer, and some other factors. Adsorption of organic molecules on electrodes causes a change of the electrode double-layer capacitance. It is the result of an exchange between the counterions and water molecules from solution, followed by changes in the dielectric properties and the thickness of the double layer on the electrode surface, that is, parameters that determine the electrode capacitance (Bockris et al., 1963 Damaskin and Petrii, 1971). 

The adsorption of organic molecules on electrode surfaces in electrolyte solutions has also long been an important subject in electrochemistry for elucidating the role of... 

The negative sign on the left-hand side is for the conformity with the convention of the faradaic current described earlier. One of the simplest models for q is the Frumkin s two-parallel-plate capacitor model [99], which has been successfully employed to describe the adsorption of organic molecules on electrodes [100],... 

The electrical double-layer (edl) properties pose a fundamental problem for electrochemistry because the rate and mechanism of electrochemical reactions depend on the structure of the metal-electrolyte interface. The theoretical analysis of edl structures of the solid metal electrodes is more complicated in comparison with that of liquid metal and alloys. One of the reasons is the difference in the properties of the individual faces of the metal and the influence of various defects of the surface [1]. Electrical doublelayer properties of solid polycrystalline cadmium (pc-Cd) electrodes have been studied for several decades. The dependence of these properties on temperature and electrode roughness, and the adsorption of ions and organic molecules on Cd, which were studied in aqueous and organic solvents and described in many works, were reviewed by Trasatti and Lust [2]. 

Other electrochemical processes of organic compounds on Pb electrodes or electrodes with UPD Pb have been studied - formaldehyde [323], oxalic acid [386], trichloro- and trifluoroethane [387], 1-phenylethylamine [388], 3-hydroxychi-nuclidine [388], dichlorodifluoromethane [389], polychlorobenzenes [390], 1-propa-nol [391], pyrrole polymerization [392], and inorganic compounds - phosphine [388] and sulfate(IV) ions [393]. Simultaneous catalytic or inhibiting influence of organic solvents - acetonitrile, dimethyl-sulfoxide, and Pb + presence on electrooxidation of small organic molecules on Pt electrodes has been studied using on-line mass spectroscopy [394],... 

In general, the adsorption of organic compounds on electrodes can be classified into two categories. In the first, the molecules adsorb but retain their chemical individuality. The adsorption bond between the molecule and the adsorbate is relatively weak, and adsorbed organic molecules may exchange readily with their peer molecules from solution ... 

Finklea, H.O. (1996). Electrochemistry of Organized Monolayers of Thiols and Related Molecules on Electrodes, in Electroanalytical Chemistry, Vol. 19, A.J. Bard and I. Rubinstein (Eds), Marcel Dekker, New York, pp. 109-120. 

Vracar L-M, Drazic DM. Adsorption and corrosion inhibitive properties of some organic molecules on iron electrode in sulfuric acid. Corros Sci 2002 44 1669. 

The interaction of CO with the solid surface produces several physical and chemical effects on the vibrational properties of the adsorbed species. The adsorption of CO can be envisaged as a two-dimensional condensation, leading to lateral coupling between adsorbed molecules. The vibrational properties of adsorbed CO can thus be used to monitor the effects of other interface properties, such as surface defects, two-dimensional phase transitions [45] and co-adsorption. Finally, CO is formed as an intermediate or poison during the oxidation of several organic molecules at electrodes, thus constituting one of the subjects of interest in electrocatalysis. 

Finklea, H. D. Electrochemistry of organized monolayers of thiols and related molecules on electrodes. In Electroanalytical Chemistry (Bard, A. J., Rubinstein, I., Eds.), Marcel Dekker, New York 1996, Vol. 19, pp. 109-335. 

The absorption of organic molecules on semiconductor surface has been drawing attention in the past years for the possibility of combining the wide range of functionahty of organic molecules with existing semiconductor-based infrastractures [7, 8]. It is also cmcial to future molecular devices since the attachment of the molecules onto the surface of electrodes also play important roles in determining the functionality of the devices [9]. 

Koch N, Kahn A, Ghijsen J, Pireaux J-J, Schwartz J, Johnson RL, Elschner A (2003) Conjugated organic molecules on metal versus polymer electrodes demonstration of a key energy level alignment mechanism. Appl Phys Lett 82 70 Cahen D, Kahn A (2003) Electron energetics at surfaces and interfaces concepts and... 

When the metal electrode has a specific adsorption of different ions and organic molecules on the surface, the value of pis perturbed from just the diffuse double layer consideration the location... 

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