Anode shielding effect

Apart from the shielding effect, signs of actual collection can also be seen on the ring CVs of Figure 4. This effect can be seen at positive ring potentials in the form of an anodic current. The anodic current is attributed to the fact that the H2O2 formed at the disk can get... 

If conforming anodes or plastics shields are to be effective they must be fairly accurately located in relation to the workpiece. The practice, common in many plating shops, of wiring the work directly to the electrical bus bars over the plating tanks is, therefore, not satisfactory. Instead, the work should be mounted on rigid jigs or racks which are then suspended from the bars over the tanks. 

The grid is charged positively with respect to the cathode, but it is less positive than the anode or collecting electrode. The grid acts to shield the collecting electrode from the effects of the positive ions and accelerates electrons toward the anode. An internal sample can be placed on the cathode or high-voltage electrode. 

The stereochemistry of the products and the regioselectivity of the coupling reaction indicates that adsorption of saturated alkyl radicals is relatively unimportant [20]. Carboxylates which are chiral and non-racemic at the a-position totally lose their optical activity in mixed heterocoupling [21, 22]. This racemization indicates either a free radical as intermediate or its fast desorption-adsorption at the anode. These findings are further supported by the decarboxylation of 3 and 4, which both form the same 1 2 1 mixture of transfrans-, cis,trans- and c ,c -coupled dimer, whilst 5-7 show a slight diastereoselectivity [23, 24]. The latter could be due to some adsorption caused by the phenyl group or double bond and/or by a more effective facial shielding of the radicals (see Chapter 3.3). 

Polymeric particles shield and block, the surface of the electrode and metal particles. Therefore, electrophoretic polarization appears, which has an appreciable effect on the process of metal electrocrystallization. The polymer is often deposited as a separate phase (liquid or solid) on the electrode surface. The polymer may cause significant kinetic restrictions to the transfer of ions, electrons, or neutral particles through this new layer. The extent of those restrictions depends on the permeability of polymeric coating. Coating the anode with an insulating polymer layer reduces the electrode activity and the current amplitude. " This inconvenience can be partly eliminated by the use of liquid electrodes, such as the dropping mercury electrode. 

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