Electrode, anode, silver

Jeanmaire D L and Van Duyne R P 1977 Part I heterocyclic, aromatic and aliphatic amines adsorbed on the anodized silver electrode J. Electroanal. Chem. 84 1-20... 

Measuring electrodes for impressed current protection are robust reference electrodes (see Section 3.2 and Table 3-1) which are permanently exposed to seawater and remain unpolarized when a small control current is taken. The otherwise usual silver-silver chloride and calomel reference electrodes are used only for checking (see Section 16.7). All reference electrodes with electrolytes and diaphragms are unsuitable as long-term electrodes for potential-controlled rectifiers. Only metal-medium electrodes which have a sufficiently constant potential can be considered as measuring electrodes. The silver-silver chloride electrode has a potential that depends on the chloride content of the water [see Eq. (2-29)]. This potential deviation can usually be tolerated [3]. The most reliable electrodes are those of pure zinc [3]. They have a constant rest potential, are slightly polarizable and in case of film formation can be regenerated by an anodic current pulse. They last at least 5 years. 

Before examining the processes in a cell, we should name the parts of a cell and clear away some language matters. The electrons enter and leave the cell through electrical conductors—the copper rod and the silver rod in Figure 12-5— called electrodes. At one electrode, the copper electrode, electrons are released and oxidation occurs. The electrode where oxidation occurs is called the anode. At the other electrode, the silver electrode, electrons are gained and reduction occurs. The electrode where reduction occurs is called the cathode. 

Jeanmaire D.L., Vanduyne R.P., Surface Raman spectro-electrochemistry. 1. Heterocyclic, aromatic, and aliphatic-amines adsorbed on anodized silver electrode, J. Electroanal. Chem. 1977 84 1-20. 

In each of the SILVER II cells, a pair of electrodes (anode and cathode) is housed in a compartment within the cell. A semipermeable membrane is placed between the electrodes. The membrane maintains electrical continuity between the electrodes and prevents mixing of the anolyte and catholyte solutions. The electrochemical cells operate at 190°F and essentially at-... 

The working electrode is silver metal. At 0% titration, the anodic limiting current is controlled by the mass transport of Cl to the electrode for the oxidation of Ag to form AgCl. As the titration proceeds, the decrease in this limiting current reflects the decrease in Cl" concentration due to addition of Ag+ titrant until the current becomes zero at the equivalence point (100% titration). 

To make the reference electrode, anodize a 5-cm-long silver wire (1 mm diameter) in a saturated KC1 solution to form AgCl. Introduce the anodized wire in a 250 pL micropipette tip through a syringe rubber piston. Fill the tip, which contains a low-resistance liquid junction, with saturated KC1 solution. 

Nowadays, the most commonly used DO electrode is the polarographic that employs an electrochemical method, through the reduction of molecular oxygen at the platinum electrode (cathode) generating electrons for the silver oxidation at the silver/silver chloride electrode (anode). In this type of sensor, it is necessary to impose an external voltage and the resulting current is measured and converted into dissolved oxygen concen-... 

Jeanmaire, D. L. and Van Duyne, R. P. (1977). Surface Raman spectroelectrochemistry Part I. Heterocyclic, aromatic, and aliphatic amines adsorbed on the anodized silver electrode. J. Electroaml. Chem. 84 1-20. Albrecht, M. G. and Creighton, J. A. (1977). Anomalously intense Raman spectra of pyridine at a silver electrode. J. Am. Chem. Soc. 99 5215-5217. Van Duyne, R. P. (1979). In Chemical and biochemical applications of lasers, Moore, C. B. (Ed.), academia press. New York, pplOl-185,... 

The so-called primary titration technique is attempted only with electrodes of silver metal, silver-silver halide, or mercury amalgams, which are the source of the electrogenerated species. The substance to be determined reacts directly at the electrode or with a reactant electrogenerated from the working electrode. This class of titrations is limited generally to non-diffusible reactants such as mercury amalgams, silver ions generated by anodization of silver metal, and halides liberated by reduction of the appropriate silver-silver halide electrode. 

A fundamental requirement for all coulometric methods is 100% current efficiency that is, each faraday of electricity must bring about chemical change in the analyte equivalent to one mole of electrons. Note that 100% current efficiency can be achieved without direct participation of the analyte in electron transfer at an electrode. For example, chloride ion may be determined quite easily using poten-tiostatic coulometry or using coulometric titrations with silver ion at a silver anode. Silver ion then reacts with chloride to form a precipitate or deposit of silver chloride. The quantity of electricity required to complete the silver chloride formation serves as the analytical variable. In this instance, 100% current efficiency is realized because the number of moles of electrons is essentially equal to the number of moles of chloride ion in the sample despite the fact that these ions do not react directly at the electrode surface. 

D. L. (eanmaire and R. P. Vanduyne, Sur-fiace Raman Spectroelectrochemistry. I. Heterocyclic, Aromatic, and Aliphatic-Amines Adsorbed on Anodized Silver Electrode,... 

Figure 2.38 - Current-potential curve of a silver electrode (cathodic branch) in a deaerated acidic solution containing Ag and Cu ions and of a zinc electrode (anodic branch) in a deaerated addic solution... 

Electrochemical methods for NO determination offer several features that are not available with spectroscopic approaches. Perhaps the most important is the capability of microelectrodes to directly measure NO in single cells in situ, in close proximity to the source of NO generation. Figure 2 shows sensors that have been developed for the electrochemical measurement of NO. One is based on the electrochemical oxidation of NO on a platinum electrode (the classical Clark probe for detection of oxygen) and operates in the amperometric mode [17]. The other is based on the electrochemical oxidation of NO on conductive polymeric porphyrin (porphyrinic sensor) [24]. The Clark probe uses a platinum wire as a working electrode (anode) and a silver wire serves as the counterelectrode (cathode). The electrodes are mounted in a capillary tube filled with a sodium chlo-ride/hydrochloric acid solution separated from the analyte by a gas-permeable membrane. A constant potential of 0.9 V is applied, and direct current (analytical signal) is measured from the electrochemical oxidation of NO on the platinum anode. In the porphyrinic sensor, NO is catalytically oxidized on a polymeric metalloporphyrin... 

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