Electrochemical oxidation of nickel in alkaline solutions: a voltammetric study and modelling

The reaction mechanisms of the oxidation of nickel in alkaline solutions has been studied by cyclic voltammetry and scanning electron micrography. It is shown that the formation of a layer of nickel hydroxide depends on the surface treatment of the nickel electrode, Even on a freshly polished electrode a hydroxide deposit was hardly obtained from an anodic polarization; cathodic prepolarization was required to obtain formation of nickel hydroxide. The quantity of nickel hydroxide electrochemically generated is related to the potential value and the duration of the cathodic treatment. The set of experimental data issued from this voltammetric study is used for comparison with the computed values obtained by digital simulation. The general multiple electrode reaction model used for these calculations is presented here. It involves the formation of nickel hydroxide according to a nucleation and growth mechanism, and redox reactions such as nickel hydroxide reversible arrow nickel oxyhydroxide, hydrogen and oxygen evolution. A reasonable fit is obtained between experimental and computed responses by introducing the values of the thermodynamic and kinetic parameters found in the literature or calculated for this purpose. (C) 1998 Elsevier Science S.A.