Galvanostatic Overpotential Transients and Electrocrystallization Processes on Copper Single Crystals in Solutions of Cupric Perchlorate

Abstract

Overpotential transients have been measured on copper single crystal surfaces oriented (100), (110), (111), and (321) undergoing galvanostatic dissolution or deposition in acidic solutions of . In the current density range 1–400 µA/cm2 it is shown that maximum values observed in over‐voltage‐time relationships respond to analytical treatment. For the (100) and (110) the anodic and cathodic overpotential maxima vs. current density relationships were symmetric about the equilibrium point, but not for the (111) and (321). From plots of certain functions of overvoltage maxima vs. current density, orientation sensitive quantities similar to exchange current densities could be calculated. At the low and intermediate current densities it was established that a “deposition anomaly” was observed on all orientations. Deposited material did not seem to occupy crystal lattice positions, and moreover, affected subsequent anodic overpotential‐time relationships in a manner related to the extent of the deposition. In situ photomicrography and goniometric observations were used to determine the orientations and rates of facet development on the various surfaces when subjected to long term deposition or dissolution, and these results are discussed in terms of the relative ease of movement of monatomic steps over the various orientations. A model is proposed of a sequence of events on the surface and in the diffusion layer which provides a self‐consistent explanation of all the experimental data.