Effect of copper ions on behavior of nickel electro-crystallization on glassy carbon electrode

Effect of 0.01 mol/L copper ions on the nickel electro-crystallization behavior on glassy carbon electrode (GCE) was investigated by means of chronoamperometry method in conjunction with the cyclic voltammetry (CV) method. The CV curves show that when 0.01 mol/L copper ions are brought into Watts solution, the peak of copper deoxidizing reaction is at potential -0.3 V (vs. SCE) or so and nickel begins to deposit at -0.75 V. Compared with Watts solution (the potential is about -0.85 V), the entering of copper ions promotes nickel electro-crystallization nucleation/growth because the existence of copper ions debases over-potential of nickel nucleation. Electro- crystallization of Watts solution with 0.01 mol/L copper ions follows Scharifker-Hill model, and the entering of copper ions doesn't change nickel electro-crystallization behavior. In the case of higher negative potential, the nucleation process of metal ion follows the instantaneous nucleation mechanism. In the case of lower negative potential, it is close to the progressive nucleation mechanism.