Solid state electrolysis

Electrotransport In this process too a super-clean atmosphere is necessary. In electrotransport (a kind of solid-state electrolysis) a large dc current (typically 200 A cm-2) is passed through a rod of the metal at a temperature 100-200°C below its melting point. In the rare earth metals the interstitial impurities slowly move towards the anode, while several metallic impurities move towards the cathode. In this case too, as in zone melting, the purest portion of the bar is its central part. 

Figure 11-16. Unstable interface (cathode) in a solid state electrolysis cell A/AX/A (e.g., Ag/AgBr/Ag).

For the solid-state reduction techniques, crystals are grown containing trivalent ions, as in the photoreduction process, but the divalents produced are now stabilized. One of these techniques involves heating the trivalent crystal with the appropriate alkaline earth metal. A convenient way of doing this is to heat the crystal with the alkaline earth metal in a vacuum so that the crystal is baked in metal vapor (11). The reduction can also be carried out by solid-state electrolysis 4,7). An electric field is applied to the crystal at an elevated temperature such as above 600°C. for calcium fluoride or above 400°C. for strontium chloride. If the reduction is carried out below these temperatures, nonuniform results are obtained. 

The properties of color centers have been most thoroughly investigated with alkali halides. From the multitude of color centers the most frequently observed ones are the so-called F-centers (from German Farbzentren) obtained either (i) by thermal treatment of alkali halides in alkali metal or halogen vapor, (ii) by irradiation with UV light, X- and y-rays as well as energy-rich protons, or (iii) by solid-state electrolysis. Only in case (i) is there a deviation from stoichiometry. 

First successful application of solid-state electrolysis to purify a ... 

For further purification of the rare earth metals electrotransport [or solid-state electrolysis (SSE) as it is sometimes called] has been the most successful technique. But it has only been demonstrated on the low vapor pressure rare earth metals (Sc,... 

Graham, C.D., 1%7, Solid State Electrolysis of Gadolinium, in 5th Rare Earth Research Conference, Vol. 5, Iowa State University, p 89. 

Sulfur and halogens are important in catalysis, being capable of behaving as poisons and promoters in different catalytic systems. A study of the effect of submonolayer quantities of these elements on the performance of several catalysts is currently in progress. Both sulfur and halogens may be conveniently and reproducibly deposited on the catalyst surface by the in situ solid-state electrolysis of the respective silver compound. 

Altunbas and Harris (1980) studied the cerium-praseodymium alloy system using electrical resistivity. X-ray diffraction and differential thermal analysis (DTA) techniques. In most of the research they used standard commercial material but some relatively pure praseodymium (purified by solid state electrolysis) was used in the DTA measurements. Appropriate amounts of the component metals were arc-melted in purified argon, turned and remelted several times. This was followed by a seven day vacuum anneal at 600°C with slow cooling to room temperature. Their electrical resistivity curves for the praseodymium sample indicated only one solid phase transformation (dhep bcc) whereas the curves for cerium and the Ce-Pr alloys exhibited two transitions, dhep fee (below 61°C for pure cerium) and fee bcc. 

Figure 1.6. Common features of Heterogeneous Catalysis, Fuel Cell operation, Electrolysis and Electrochemical Promotion 1. Solid state catalyst, 2. Adsorption, 3. AG < 0, 4. Yield control via DC current or voltage application (Adapted from N. A. Anastasijevic).

Decarboxylation of p-lactones (see 17-27) may be regarded as a degenerate example of this reaction. Unsymmetrical diacyl peroxides RCO—OO—COR lose two molecules of CO2 when photolyzed in the solid state to give the product RR. Electrolysis was also used, but yields were lower. This is an alternative to the Kolbe reaction (11-37). See also 17-29 and 17-40. 

It is a toxic colourless gas which is dangerously explosive in the gaseous, liquid and solid states [1]. It is produced dining electrolysis of nitrogenous compounds in hydrogen fluoride [2], Later work (perhaps with purer material ) did not show the explosive instability [3], The shock-sensitivity is confirmed [4],... 

In the most recent plants, the electrolysis is performed in a membrane cell while the chemical step is carried out by allowing the chromic acid to trickle through a column of solid anthracene. The product - anthraquinone - is also insoluble in the aqueous acid so that the organic conversion is effectively completed in the solid state. The reaction goes to completion provided the particle size of the anthracene falls within a suitable range. The spent redox reagent is then passed through an activated carbon bed to remove traces of... 

If the actinide metal is available in sufficient quantity to form a rod or an electrode, very efficient methods become applicable eiectrorefining, zone melting, solid state electrotransport. Thorium, uranium and plutonium have been refined by electrolysis in molten salts An electrode of impure metal is dissolved anodically in a molten salt bath, e.g. in LiCl-KCl eutectic the purified metal is deposited on the cathode as a solid or a liquid. 

Solid state materials that can conduct electricity, are electrochemically of interest with a view to (a) the conduction mechanism, (b) the properties of the electrical double layer inside a solid electrolyte or semiconductor, adjacent to an interface with a metallic conductor or a liquid electrolyte, (c) charge-transfer processes at such interfaces, (d) their possible application in systems of practical interest, e.g. batteries, fuel cells, electrolysis cells, and (e) improvement of their operation in these applications by modifications of the electrode surface, etc. 

Dithiazolium cations can be readily reduced to the stable mono- and diradicals. Reaction of the disalt 43 could be effected, on a milligram scale, by electrolysis in an acetonitrile solution at 50 pA onto Pt wire cathode <1997JA2633>. Larger quantities could be obtained by chemical reduction. Attempts to reduce cation 43 directly with silver or zinc powder were unsuccessful. The most successful approach involved the use of triphenylantimony as reducing agent and bis(triphenylphosphine)iminium chloride ((PPN)Cl Equation (5)). The product obtained (7) is remarkably stable in the solid state, in air, and in organic solutions. 

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