Cathodes nickel

A 600-ml., tail-form beaker is equipped with a thermometer, a magnetic stirring bar, and two electrodes. A 45-mesh cylindrical platinum anode (Note 1) is used. Surrounding the anode is a cylindrical nickel cathode (Note 2). The electrodes are held in place (distance between anode and cathode 0.75 cm.) and suspended in the beaker by means of a clamp formed from Delrin rods (Note 3). The electrodes are connected to an adjustable d.o. power supply (Notes 4, 5). 

The nickel cathode, fashioned from 22 gauge nickel sheet obtained from Huntington Alloys, Inc., Huntington, W. Va. 25720, had a height of 5.6 cm. and a diameter of 6.6 cm. When the sheet v/aa rolled into a cylinder a small gap was left at the seam. 

Another application of the electrolysis of tantalum and niobium in fluoride melts is in the preparation of intermetalic compounds as a result of the interaction between the electrochemically precipitating metal and the cathode material. Based on an investigation of the electrochemical reduction of K2TaF7 or K2NbF7 in a LiF - NaF melt on nickel cathodes, Taxil and Qiao [565] determined the appropriate conditions for the formation of TaNi3 or NbNi3 in the form of stable phases in the bulk of the obtained layer. 

Pressure = 0.3 mm Hg nickel cathode % yield refers to % total ions observed... 

Figure 6. Glow discharge in nitrogen Pressure = 0.3 mm Hg nickel cathode ions are sampled from the cathode % yield refers to % total ions observed. At very low discharge currents the distinct glow in front of the cathode disappears, and a continuous glow corona) is obtained throughout the discharge tube...

Bockris, J. O M. and Potter, E. C. (1952) The mechanism of hydrogen evolution at nickel cathodes in aqueous solutions. 

Figure 5.8 Outokumpu process for nickel cathode production.

The stereochemistry of electrochemical reduction of acetylenes is highly dependent upon the experimental conditions under which the electrolysis is carried out. Campbell and Young found many years ago that reduction of acetylenes in alcoholic sulfuric acid at a spongy nickel cathode produces cis-olefins in good yields 126>. It is very likely that this reduction involves a mechanism akin to catalytic hydrogenation, since the reduction does not take place at all at cathode substances, such as mercury, which are known to be poor hydrogenation catalysts. The reduction also probably involves the adsorbed acetylene as an intermediate, since olefins are not reduced at all under these conditions and since hydrogen evolution does not occur at the cathode until reduction of the acetylene is complete. Acetylenes may also be reduced to cis olefins in acidic media at a silver-palladium alloy cathode, 27>. 

Doped Nickel Cathode Alloy Anode Low Cost... 

Quite recently, Troupel et al. have developed an effective synthesis of gem-difluoro-/ -oxonitriles using an electrogenerated base derived from phenyl bromide and a sacrificial magnesium anode together with a nickel cathode coated with a small deposit of cadmium as shown in Scheme 4.5 [34]. 

Alkynes can be reduced electrolytically. Internal alkynes gave 65-80% yields of cis alkenes when electrolysed in 10% sulfuric acid in ethanol at spongy nickel cathode [127], or predominantly trans alkenes if the electrolysis was carried out in a methylamine solution of lithium chloride. The yields of the alkenes and the ratios of trans to cis alkenes varied depending on whether the electrolysis was carried out in divided or undivided cells (yields 24-80%, composition of product 89-99% of trans alkene) [379]. 

Arylalkenes [23] and alkenes with electron withdrawing substituents [24] can be bis-alkylated across the alkene bond by electrochemical reaction with dflialoal-kanes giving 3- to 6-membered carbocyclic products in good yields. ITie best reaction conditions use an undivided cell with a nickel cathode and a sacrificial aluminium anode in dimethylformamide or N-methylpyrrolidone containing a tetraalkylammonium salt. Anodically generated aluminium ions are essential for the reaction. 1,2-Disubstituted alkenes, regardless of their stereochemistry, are converted to the tranj-substituted cycloalkane. 

Reduction of substituted nitrobenzenes under alkaline conditions, usually with aqueous sodium acetate as electrolyte and a nickel cathode, is the classical method due to Elbs [45] for the formation of azo- and azoxy-compounds. Protons are used in the electrochemical reaction so that the catholyte becomes alkaline and under these conditions, phenylhydroxylamine reacts rapidly with nitrosobenzene to form azoxybenzene. Finely divided copper has long been known to catalyse the reduction of nitrobenzene to aniline in alkaline solution at the expense of azoxybenzene production [46]. Modem work confirms that whereas reduction of nitrobenzene at polycrystalline copper in alkaline solution gives mainly azoxybenzene, if the electrode is pre-oxidised in alkaline solution and then reduced just prior to the addition of nitrobenzene, high yields of aniline are obtained with good current efficiency... 

Although it has been known for more than a century that large amounts of hydrogen can be loaded into nickel cathodes by electrolysis [68, 69], systematic work on the Ni H2 system was only initiated much later. 

The electrochemical reduction of bromotrifluoromethane (CF3Br) in DMF in a cell fitted with a sacrificial zinc anode and a stainless steel or nickel cathode is a typical case where the organometallic compound formation can be realized according to two different processes, and where a transient species having a different reactivity compared to usual organometallics can be produced. 

For a long time it has been industrial practice to activate nickel cathodes by depositing coatings of nickel sulfide on their surface. Two different methods are used cathodic deposition of NiS, and chemical sulfidization of nickel electrodes. 

Fig. 14. Comparison of the current-voltage curves of a smooth nickel cathode and two different Raney-nickel-coated cathodes posessing comparable loading and effective surface (a) smooth nickel. Raney nickel prepared from two different precursors (b) plasma-sprayed NiAh, (c) NiAU cold rolled together with Mond nickel.

Very little systematic work has been conducted with Raney-nickel cathodes. Junghans reported on electrocatalytic hydrogenation of steroids, and he stresses that electrohydrogenation with Raney nickel yields higher selectivities (tram- vs cis-hydrogenation) than the usual catalytic hydrogenations (202, 203). 

Nickel, used to make stainless steel, can be purified by electrorefining. The electrolysis cell has an impure nickel anode, a pure nickel cathode, and an aqueous solution of nickel sulfate as the electrolyte. How many kilograms of nickel can be refined in 8.00 h if the current passed through the cell is held constant at 52.5 A ... 

The electrochemical reduction of acid chlorides takes a very different course when carried out in an undivided cell equipped with nickel cathode and anode79. The product is a symmetrical ketone (57) 57 is formed by a complex sequence involving both electrodes (Scheme 12). This is really a chemical reaction induced by a highly reactive form of nickel produced by dissolution of the anode and plated onto the cathode. We have already encountered similar chemistry involving highly reactive zinc (Section V.A.l). 

The electrolysis of P-diketone solutions in ethanol (0.4-0.6 M) was carried out using a uranium anode and nickel cathode for 3-5 hr at 45-60 mA in an inert atmosphere (Ar, He) as in an oxidative one (02, dry air) with agitation. LiCl was used as supporting electrolyte (O.lmol/L). P-Diketones [acetylacetone (Hacac) and benzoylacetone (Hba)] were distilled before use. 

Electrolytic sulphuric acid 3 is produced and a concentration as high as 95 per cent, obtained by oxidising sulphurous acid in a diaphragm cell with a cylindrical nickel cathode and an anode of platinum gauze. A porous cup or cell which acts as cathode is filled with sulphuric acid or sodium sulphite, and the outer anode compartment contains a solution of sulphur dioxide which is kept saturated during the process by passing in the gas COn-... 

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