Cadmium, electrodeposition

Tellurium and cadmium Electrodeposition of Te has been reported [33] in basic chloroaluminates the element is formed from the [TeCl ] complex in one four-electron reduction step, furthermore, metallic Te can be reduced to Te species. Electrodeposition of the element on glassy carbon involves three-dimensional nucleation. A systematic study of the electrodeposition in different ionic liquids would be of interest because - as with InSb - a defined codeposition with cadmium could produce the direct semiconductor CdTe. Although this semiconductor can be deposited from aqueous solutions in a layer-by-layer process [34], variation of the temperature over a wide range would be interesting since the grain sizes and the kinetics of the reaction would be influenced. 

The other method is cadmium electrodeposition on a nickel-plated steel foil (serving as current collector) using a plating bath containing acidified cadmium sulfate (type AB2C3). In this case the user is supplied with a battery in charged ( ready for use ) condition. 

The cadmium electrodeposition on the solid cadmium electrode from the sulfate medium was investigated [217]. The following kinetic parameters were obtained cathodic transfer coefficient a = 0.65, exchange current density Iq = 3.41 mA cm , and standard rate constant kg = 8.98 X 10 cm s . The electrochemical deposition of cadmium is a complex process due to the coexistence of the adsorption and nucleation process involving Cd(II) species in the adsorbed state. 

The cadmium electrodeposition on the cadmium electrode from water-ethanol [222, 223], water-DMSO [224], and water-acetonitrile mixtures [225-229] was studied intensively. It was found that promotion of Cd(II) electrodeposition [222] was caused by the formation of unstable solvates of Cd(II) ions with adsorbed alcohol molecules or by interaction with adsorbed perchlorate anions. In the presence of 1 anions, the formation of activated Cd(II)-I complex in adsorbed layer accelerated the electrode reaction [223]. 

The effect of perchlorate ions on cadmium electrodeposition was investigated in water-AN mixtures [227, 228]. The formation of ionic associates in the surface layer inhibited cadmium electrodeposition, and promoted the formation of higher quality coatings. 

The same authors have found that the inhibition effect of crown ethers [230] and crown esters [229] on cadmium electrodeposition from water-AN mixtures was caused by the competitive adsorption of macrocycles and organic solvents molecules. The effect of structure and concentration of crown ethers on the cadmium electrodeposition from aqueous sulfate solutions was also studied [231]. 

The polarization curves for nickel, copper, and cadmium electrodeposition (in all solutions, concentrations of depositing ions were 0.070 M) are shown in Fig. 1.13, while corresponding Tafel plots and the results of linear polarization experiments... 

Fig. 2.16 The dependence of the overpotential on time during cadmium electrodeposition on a spiral platinum cathode (electrode surface area 1.5 cm ) from 0.50 M CdS04. The deposition current was 65 pA, is the nucleation, rjcr is the crystallization, and rj is the deposition overpotential (Reprinted from Ref. [47] with permission from Bulgarian Chemical Communications and Ref. [13] with kind permission from Springer)...

The effect of organic compounds on morphology of electrodeposited metal has been examined by the analysis of cadmium electrodeposition processes from solution containing 0.25 M CdS04 in 0.50 M H2SO4 to which was added 3.3 g dm poly(oxyethylene alkylphenol) (9.5 mol ethylene oxide) [68]. 

Hippensteel, C. L., and Borgmann, C. W. (1930). Outdoor atmosphere corrosion of zinc and cadmium electrodeposited coatings on iron and steel. Trans. Am. Electro-chem. Soc., 58, 23-41. 

QQ-P-416, Federal Specification Plating Cadmium (Electrodeposited), IBR approved for 1926.104(e). 

Typical spongy electrodeposits are formed during zinc and cadmium electrodeposition at low overpotentials [7,74]. Scanning electron microscopy images of zinc deposited at an overpotential of 20 mV onto a copper electrode from an alkaline zincate solution are shown in Fig. 1.27. 

An important result following from the theoretical equations (2.135 ) and (3.19) is that the probability Pf of the inflection point of a non-stationary P (t) transient cannot exceed the value of l-exp(-l/2) 0.3935... (see the fifth column of Table 3.1). This means that the theoretical model accounting for the site birth effect cannot explain the results of Gunawardena et al. [3.10] and of Toshev and Markov [3.20] who have obtained probabilistic transients with Py 0.5 in the case of mercury and cadmium electrodeposition on a platinum surface. An interpretation on the basis of the macroscopic Zeldovich-Frenkel approach is rather questionable, too, because the size of the critical nuclei in these experiments is very small. Since the formation of an oxide coverage seems unlikely under the conditions of those experiments it might be possible to associate the observed non-stationary effects with the reconstmction of preformed UPD layers after applying the nucleation overpotential [3.25, 3.26]. Such complex electrochemical processes are certainly of major importance for the nucleation kinetics but their mechanism is not fully clarified. 

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