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Chemistry

Optimization of Electrolytic Production of Nickel

Grzegorz Szymanski (Research Associate)
It is known that the rate and mechanism of a metal electrodeposition reaction depends strongly on nature of anions present in the electrolytic bath. It is also known that organic additives display a polishing and levelling effect by increasing the density of nuclei in the deposited layer and/or by slowing down the rate of deposition at elevations relative to the rate of deposition on the recesses of the rough surface. The organic surfactants therefore reduce surface roughness, and as a consequence, avoid electrolyte and solid particle entrapment in the deposited metal. Such entrapment has negative effects on metal purity and on technical uses to which such metal may be employed.
The general objective of this project is to provide fundamental understanding of the electrochemical deposition of nickel from mixed sulphate-chloride electrolytes. The specific objectives of the project are:(i) to determine differences between the quality of the deposits produced by electrolysis from electrolytes of different compositions, (ii) to understand the role played by organic additives in reducing pitting and improving levelling, (iii) to optimize the conditions needed for production of low stress and smooth nickel deposit.
To achieve these objectives we will determine how (i) the composition of the electrolyte, (ii) the nature of the additive, (iii) the concentration of the additive:
- influence the rates of Ni electrodeposition and the rates of parasitic processes such as hydrogen evolution and oxygen reduction;
- affects the rate of nucleation of Ni deposits and the growth and morphology of the deposited layers.
All investigations of the kinetics of Ni deposition, hydrogen evolution and oxygen reduction are performed using the rotating disk electrode and potential/current step experiments.
The Electrochemical Atomic Force Microscopy (EC-AFM) is employed to study the effect of adsorption of anions and organic additives on the rate of nucleation and growth of deposited nickel.