PECULIARITIES OF ELECTRODEPOSITION OF COBALT—WOLFRAM—RENIUM ALLOY

The methods of stationary voltammetry and chronovoltammetry have been used to study deposition processes of ternary CoWRe alloys at different rhenium content of the electrolyte and deposition current density. It has been found that the limiting currents have a diffusive nature and are proportional to the concentration of perrhenate ions in the electrolyte. The CoWRe alloys should be formed by the discharge of bimetallic citrate complexes of the following composition [(Co)(WO4)(H)(Cit)]2- and rhenium electrodeposition. Rhenium does not form complexes with citrate ions and deposits better in an alloy with iron group metals than in the form of an individual metal from a perrhenate solution. It can be assumed that the discharge of rhenium into the alloy occurs from a surface complex, the nature of which has not yet been established. The alloy current efficiency reaches 93% due to the high overpotential of hydrogen evolution on the alloy surface. According to the results of investigations of the catalytic properties of alloys in the hydrogen reduction reaction, it has been found that with increasing the rhenium content of the electrolyte and alloy, an increase in hydrogen overpotential is observed. Based on the Tafel coefficients found, it was found that in an acidic and neutral medium, the limiting stage of the cathodic and anodic reaction is the transfer of the first electron. In an alkaline medium, the anode process is complicated by the simultaneous transport of two electrons. The found values of corrosion resistance are 1-2 kOm·cm-2 in solutions of 0.01 M H2SO4; 20-110 kOm·cm-2 in 2.5% NaCl; 10-30 kOm·cm-2 in 1.0 M KOH. Based on the dependence of corrosion resistance on the refractory metals content of the alloy and the electrodeposition conditions, the optimum deposition current density of 10 mA·cm-2 has been found.

Electrochemical Properties of Zinc-LaCoO3 Electrode for Alkaline Zinc-Based Battery

The electrochemical behaviors of zinc anode in the presence of the additives added to the electrodes are presented. LaCoO3 was used as an additive to improve the electrochemical properties of the zinc anode. LaCoO3 synthesized by sol gel method (Schiff base complex) was added to Zn and ZnO powder with the weight ratios of 1:0.05 and 1:0.002 respectively. The electrochemical properties of the zinc and zinc/LaCoO3 electrodes in 6M KOH solution were investigated by voltammetric technique and electrochemical impedance spectroscopy (EIS). The cyclic voltammograms showed that zinc electrodes with LaCoO3 additive gave higher anodic currents and ZnO passivation delayed. The cathodic Tafel plot indicated that the hydrogen overpotential shifted toward more negative value. The EIS revealed that the charge transfer resistances of the zinc/LaCoO3 electrodes were higher than that of zinc electrodes.