Impedance measurements for nickel deposition in sulfate and chloride electrolytes
Résumé
From the analysis of the impedance of nickel deposition, the electrode kinetics is shown to be dependent on the type of anion. In chloride electrolytes a slow electrode activation with cathodic polarization is predominant. In sulfate solutions a low-frequency capacitive feature, favored by a pH decrease, appears to result from interactions between the nickel and hydrogen discharges. An interpretation is proposed where the ad-ion NiadsI acts as both a reaction intermediate and a catalyst associated with a propagating kink site, and where the adsorbed species Hads*, generated by the presence of NiadsI, inhibit the hydrogen evolution. It is concluded that the active area is closely connected to the coverages by adsorbates.