Effect of glassy carbon, gold, and nickel electrodes on nickel electrocrystallization in an industrial electrolyte

Abstract

The effects of three different substrate materials (glassy carbon, gold, and nickel electrodes) on the electrocrystallization behavior of nanocrystalline nickel in an industrial electrolyte with complex compositions were studied by cyclic voltammetry (CV), single potential step chronoamperometry. The CV results indicated that the initial deposition potentials of nickel shift to the positive direction in the order glassy carbon < gold < nickel electrodes, while the nickel deposition overpotential decreased at the same time. Chronoamperometry results indicated that from the glassy carbon to gold and nickel electrodes, the adhesion of nickel nanoparticles on the electrodes increased, nucleation relaxation time became shorter, and the number of nuclei decreased. As the deposition potential is negatively shifted and the deposition time is prolonged, the I-t curves for the nickel and gold electrodes are more stable and reliable than those from the glassy carbon electrodes. The chronoamperometric study combined with SEM revealed that the nucleation mechanism of nickel on different substrates changed from three-dimensional progressive to instantaneous, but the time of the transition is different. When the deposition time is 100 s, the nanocrystalline nickel deposited on the nickel and gold electrodes has good integrity and uniformity. This was also confirmed in studies using atomic force microscopy and transmission electron microscopy. Moreover, the results of transmission electron microscopy (TEM) show that there are many twins in the nanocrystalline nickel layer deposited on the gold electrode at −0.95 V, 100 s. The electrocrystallization process of nickel is complicated by the complex ionic components in the industrial electrolyte of the nickel sulfide soluble anode/mixed acid system.