Electrochemistry anode

A galvanic current is the same as a DC current, and the term is used in particular for therapeutic applications and in electrochemistry. Anode and cathode are not defined from voltage polarity, but current direction. A galvanic (electrolytic) cell produces (passes) DC. If it does not, it is a dielectric cell and only displacement AC passes. Even so, an in-phase current may pass the cell, but it is due to dielectric losses and not DC conductance. Thus in-phase components are not the same as DC components. 

It must be noted that impurities in the ionic liquids can have a profound impact on the potential limits and the corresponding electrochemical window. During the synthesis of many of the non-haloaluminate ionic liquids, residual halide and water may remain in the final product [13]. Halide ions (Cl , Br , I ) are more easily oxidized than the fluorine-containing anions used in most non-haloaluminate ionic liquids. Consequently, the observed anodic potential limit can be appreciably reduced if significant concentrations of halide ions are present. Contamination of an ionic liquid with significant amounts of water can affect both the anodic and the cathodic potential limits, as water can be both reduced and oxidized in the potential limits of many ionic liquids. Recent work by Schroder et al. demonstrated considerable reduction in both the anodic and cathodic limits of several ionic liquids upon the addition of 3 % water (by weight) [14]. For example, the electrochemical window of dry [BMIM][BF4] was found to be 4.10 V, while that for the ionic liquid with 3 % water by weight was reduced to 1.95 V. In addition to its electrochemistry, water can react with the ionic liquid components (especially anions) to produce products... 

Faraday developed the laws of electrolysis between 1831 and 1834. In mid-December of 1833. he began a quantitative study of the electrolysis of several metal cations, including Sn2+, Pb2+, and Znz+. Despite taking a whole day off for Christmas, he managed to complete these experiments, write up the results of three years work, and get his paper published in the Philosophic Transactions of the Hoyal Society on January 9,1834. In this paper, Faraday introduced the basic vocabulary of electrochemistry, using for the first time the terms "anode," cathode," ion, "electrolyte," and "electrolysis."... 

Pulsed amperometric detection (PAD), introduced by Johnson and LaCourse (64, 65) has greatly enhanced the scope of liquid chromatography/electrochemistry (66). This detection mode overcomes the problem of loss of activity of noble metal electrodes associated with the fixed-potential detection of compounds such as carbohydrates, alcohols, amino acids, or aldehydes. Pulsed amperometric detection couples tlie process of anodic detection with anodic cleaning and cathodic reactivation of a noble metal electrode, thus assuring a continuously cleaned and active... 

The limited anodic potential range of mercury electrodes has precluded their utility for monitoring oxidizable compounds. Accordingly, solid electrodes with extended anodic potential windows have attracted considerable analytical interest. Of the many different solid materials that can be used as working electrodes, the most often used are carbon, platinum, and gold. Silver, nickel, and copper can also be used for specific applications. A monograph by Adams (17) is highly recommended for a detailed description of solid-electrode electrochemistry. 

Voltammograms of a polythiophene film showing reasonably reversible electrochemistry of both types are shown in Fig. 2.M The formal potentials (average of the anodic and cathodic peak potentials) for p- and n-doping can provide useful estimates of the energies of the polymer s valence and conduction bands and its band gap35... 

DespiC, A. Electrochemistry of Aluminum in Aqueous Solutions and Physics of Its Anodic Oxide 20... 

G. Foti, D. Gandini, and C. Comninellis, Anodic oxidation of organics on thermally prepared oxide electrodes, Current Topics in Electrochemistry 5, 71-91 (1997). 

As in aqueous electrochemistry it appears that application of a potential between the two terminal (Au) electrodes leads to charge separation on the Pt film so that half of it is charged positively and half negatively8 thus establishing two individual galvanic cells. The Pt film becomes a bipolar electrode and half of it is polarized anodically while the other half is polarized cathodically. The fact that p is smaller (roughly half) than that obtained upon anodic polarization in a classical electrochemical promotion experiment can be then easily explained. 

It was also observed that, with the exception of polyacetylene, all important conducting polymers can be electrochemically produced by anodic oxidation moreover, in contrast to chemical methoconducting films are formed directly on the electrode. This stimulated research teams in the field of electrochemistry to study the electrosynthesis of these materials. Most recently, new fields of application, ranging from anti-corrosives through modified electrodes to microelectronic devices, have aroused electrochemists interest in this class of compounds... 

The properties of anodic layers of HgS formed on mercury in sulfide solutions have been investigated in comparison with anodic sulfide layers of cadmium and bismuth. Also, the electrochemistry of mercury electrodes in aqueous selenite solutions has been studied (see Sect. 3.2.1). The problem with the presence of several cathodic stripping peaks for HgSe in acidic Se(IV) solutions has been addressed using various voltammetric techniques at a hanging-mercury-drop electrode [119]. 

The electrochemistry of single-crystal and polycrystalline pyrite electrodes in acidic and alkaline aqueous solutions has been investigated extensively. Emphasis has been laid on the complex anodic oxidation process of pyrite and its products, which appears to proceed via an autocatalytic pathway [160]. A number of investigations and reviews have been published on this subject [161]. Electrochemical corrosion has been observed in the dark on single crystals and, more drastically, on polycrystalline pyrite [162]. Overall, the electrochemical path for the corrosion of n-EeS2 pyrite in water under illumination has been described as a 15 h" reaction ... 

Itaya, K., Atomic-scale aspects of anodic dissolution of metals studies by in situ scanning mnneling microscopy, in Interfacial Electrochemistry, A. J. Wieckowski, Ed., Marcel Dekker, New York, 1999, p. 187. 

The oxides often are nonstoichiometric (with an excess or dehcit of oxygen). Many oxides are semiconducting, and their conductivity can be altered by adding various electron donors or acceptors. Relative to metals, the applications of oxide catalysts in electrochemistry are somewhat limited. Cathodic reactions might induce a partial or complete reduction of an oxide. For this reason, oxide catalysts are used predominantly (although not exclusively) for anodic reactions. In acidic solutions, many base-metal oxides are unstable and dissolve. Their main area of use, therefore, is in alkaline or neutral solutions. 

See the NACE Papers Oliver W. Siebert, Correlation of Laboratory Electrochemical Investigations with Field Applications of Anodic Protection, Materials Performance, vol. 20, no. 2, pp. 38-43, February 1981 Anodic Protection, Materials Performance, vol. 28, no. 11, p. 28, November 1989, adapted by NACE from Corrosion Basics— An Introduction. (Houston, Tex. NACE, 1984, pp. 105-107) J. Ian Munro and Winston W. Shim, Anodic Protection— Its Operation and Appheations, vol. 41, no. 5, pp. 22-24, May 2001 and a two-part series, J. Ian Munro, Anodic Protection of White and Green Kraft Liquor Tankage, Part I, Electrochemistry of Kraft Liquors, and Part 11, Anodic Protection Design and System Operation, Materials Performance, vol. 42, no. 2, pp. 22-26, February 2002, and vol. 42, no. 3, pp. 24-28, March 2002. 

Electrochemistry voltammetry, anodic stripping (ASV), cathodic stripping (CSV), polarography, differential pulse polarography (DPP), ion selective electrode (ISE)... 

Watanabe M, Igarashi H, Fujino T. 1999. Design of CO tolerant anode catalysts for polymer electrolyte fuel cell. Electrochemistry 67 1194-1196. 

Figure 12.13 Electrochemistry and kinetics of CO resulting from methanol decomposition on polycrystalline Pt with O.IM H2SO4 electrol3de and 0.1 M methanol, (a-d) Current, SFG amphtude, frequency, and width of adsorbed CO, scanning the potential in both directions as indicated with the solid hne and fiUed circles denoting the forward (anodic) scan and the dashed hne and unfilled circles denoting the back (cathodic) scan, (e-g) Starting at 0.6 V, where the adsorbed CO is rapidly electro-oxidized, the potential is suddenly jumped to 0.2 V. The reformation of the CO layer (CO chemisorption) due to methanol decomposition occurs in about 20 s. The adsorbed CO molecules are redshifted, and have a broader spectrum at shorter times, when the adlayer coverage is low.

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