Voltammetric study of a catalytic electrode process with parallel complexation reaction. Reduction of the nickel ion in the presence of nicotinamide

The reduction of Ni ion on a static Hg-drop electrode in the presence of nicotinamide was studied by linear-scan voltammetry. Under these conditions, the main Ni peak is preceded by a wave due to reduction of Ni ion catalyzed by nicotinamide (E1/2 = -0.78 V vs. SCE). The catalytic reduction is a steady-state process if the scan-rate is low and the Ni ion is in excess. It was assumed that the complex NiL2+ (L = nicotinamide) is the reducible species and the regeneration of this compound by a chem. reaction gives the electrode process the catalytic character. The kinetic equations founded on this mechanism are in fair agreement with the experimental data and enables calculating the equilibrium (log K1 = 3.45) and rate (∼1.2 × 104 mol-1 L s-1) constants for the formation of NiL2+.