Electrodes, oxidation-reduction solubility method

The first SERS spectra were recorded on a roughened silver surface prepared by the method of EC-oxidation/reduction cycles [23]. By application of an oxidation potential to the metal electrode, the electrode was oxidized to soluble ions or an insoluble surface complex a reduction potential will then reduce these species at the surface, forming surface nanostructures. As silver is one of the most extensively studied SERS substrate materials, it is reasonable to take this as an example to illustrate the oxidation/reduction cycles procedure in detail [88]. 

For the rapid determination of Tc in a mixture of uranium fission products. Love and Greendale have used the method of amalgam polarography. It consists in a selective reduction of technetium at a dropping mercury electrode at a potential of —1.55 V vs. SCE in a medium of 1 M sodium citrate and 0.1 M NaOH. Under these conditions, technetium is reduced to an oxidation state which is soluble in mercury. The amalgam is removed from the solution of fission fragments and the amount of Tc determined in nitric acid solution of the amalgam by a y count. For Tc the measurement accuracy is within 1 %, and the decontamination factor from other fission products 10 . 

However, it is recognized that slightly soluble intermediates such as CdO(OH) and Cd(OH)3 are involved. Cadmium does not corrode since its equilibrium potential is more positive than that of hydrogen in the same solution. The active material in pocket plate cells consists of metallic cadmium, with up to 25% of iron and small quantities of nickel and graphite to prevent agglomeration. Two methods of preparation are used. One involves the electrochemical co-reduction of a solution of cadmium and iron sulphate in the other, dry mixtures of cadmium oxide or hydroxide and Fe304 or iron powder are used. In some methods of pocket plate manufacture, the electrode material is pressed into pellets or briquettes before being inserted into the pockets, and various waxes or oils may be used to facilitate this process. 

An electrode is inexpensive when compared with most chemical reagents. It is immobile, and thus causes less environmental and solubility problems than most chemical oxidants and reductants. It can change the polarity of reagents by oxidation or reduction ( Redox-Umpolung ) and in this way can shorten synthetic sequences. Controlled potential electrolysis allows the selective conversion of one out of several electrophores in a molecule. A technical scale-up causes in most cases lesser problems than the scale-up of a chemical reaction. These advantages and the wide choice of conversions have made electrolysis today at least for those that take the small effort to assemble an electrolysis cell and connect it to a d.c. power supply - to an attractive alternative and supplement for chemical synthetic methods. 

Voltammetric/polarographic methods are not very important for anion analysis. Only bromate, iodate, and periodate can be determined by means of polarographic reduction currents. Indirect determinations are possible for those anions that form compounds of low solubility or stable complexes with the Hg ions formed in the anodic oxidation of the electrode mercury. The current caused by the dissolution of the mercury is proportional to the concentration of these anions in the sample... 

Two parts are treated one is the physical and chemical features of materials of molten carbonate fuel cells (MCFCs), and the other is performance analysis with a 100 cm class single cell. The characteristics of the fuel cell are determined by the electrolyte. The chemical and physical properties of the electrolyte with respect to gas solubility, ionic conductivity, dissolution of cathode material, corrosion, and electrolyte loss in the real cell are introduced. The reactirm characteristics of hydrogen oxidation in molten carbonates and materials for the anode of the MCFC are reviewed. The kinetics of the oxygen reduction reaction in the molten carbonates and state of the art of cathode materials are also described. Based on the reaction kinetics of electrodes, a performance analysis of MCFCs is introduced. The performance analysis has importance with respect to the increase in performance through material development and the extension of cell life by cell development. Conventional as well as relatively new analysis methods are introduced. 

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