Partial currents of anodic oxidation of copper in alkaline media according to RRDE data. II. Experiment

Anodic oxidation of copper in aqueous alkaline media is studied using the method of chronoamperometry on a rotating ring–disk electrode in a wide range of potentials. Partial currents of processes of anodic oxide formation, active copper dissolution, and chemical dissolution of Cu(I) oxide taking into account the possibility of its chemical growth are calculated. The current of chemical oxide dissolution is registered at all the studied potentials. In the cathodic range of potentials, anodic dissolution of copper is thermodynamically impossible, but, after the disk electrode polarization is switched off, oxide is formed via the chemical route. In the range of potentials where anodic copper dissolution is thermodynamically possible, the current of anodic oxide formation prevails over the currents of the other partial processes. The dependence of partial currents on time within the studied time interval (120 s) is not systematic, while their dependence on the disk polarization potential is very significant: the rate of oxide formation repeats the shape of the cyclic voltammogram, the rate of active copper dissolution through the oxide pores increases with potential, and the rate (and rate constant) of chemical dissolution of Cu(I) oxide are maximum at the potentials of its anodic formation. If the thermodynamic activity of the oxide layer does not reach unity within the anodic oxidation period, then the rate constant of chemical copper oxidation exceeds the rate constant of chemical oxide dissolution. The result is chemical oxidation of copper by traces of molecular oxygen in the solution.