Fig nbsp shows the cyclic voltammetry curves obtained at xA
Fig. 1 shows the cyclic voltammetry curves obtained at 30 °C by adding different concentrations of Zn2 + to the bath; the cathodic potential sweep was reversed at − 1100 mV. Nickel deposition from the bath without zinc starts at about − 850 mV (Fig. 1a, curve 1), in agreement with the results of Lin and Selman . As pointed out by the same authors, this potential, almost 500 mV more negative than the standard equilibrium potential of nickel, indicates that extra ITMN191 is needed to overcome the barrier of heterogeneous deposition onto foreign substrate. The addition of Zn2 + leads to a strong decrease in the cathodic current density, indicating a remarkable inhibition of Ni reduction. The addition of 1 and 10 mM Zn2 + (curves 2 and 3) shifts the start of deposition to − 890 and − 1020 mV respectively. In all the curves in Fig. 1a, the forward and the reverse scans form a relatively large loop, due to the fact that both pure Ni and Ni–Zn alloy deposition current densities during the forward scan are lower than during the reverse scan. This indicates that the electrodeposition on the freshly deposited nickel or Ni–Zn alloy surface required less energy than on glassy carbon. With 1 mM Zn2 + in the bath (Fig. 1a, curve 2), the shape of the anodic curve is similar to that obtained from the pure Ni bath (Fig. 1a, curve 1) and shows only one wide peak (a1) at − 120 mV. This indicates microspore mother cell a solid solution of Zn in the fcc nickel lattice was deposited and that the presence of a low Zn percentage does not change the electrochemical characteristics of the deposited nickel. Also Fleischmann and Saraby-Reintjes  reported that α-Ni dissolves during the potential-sweep stripping with a current density peak around − 100 mV vs SCE. With 10 mM Zn2 + in the bath (Fig. 1a, curve 3), during the reverse scan, the current density forms a plateau in the range from − 1010 to − 800 mV, while the anodic curve (inset in Fig. 1a) shows a new peak at about − 380 mV (a2). A similar cathodic plateau has been observed also by Lin and Selman in chloride-acetic bath . On increasing Zn2 + concentration up to 50 mM (Fig. 1b, curve 1), the cathodic current density becomes very low (about 0.33 mA cm− 2 at − 1100 mV) and only a very small anodic peak at about − 600 mV can be observed, indicating that the alloy deposition is almost completely inhibited and that the cathodic current density is mainly due to the hydrogen reduction. A further decrease in the cathodic current density has been found on increasing the Zn2 + concentration to 100 mM (Fig. 1b, curve 2).