PHOTOELECTROCHEMICAL CHARACTERIZATION OF THE ANODIC FILM ON ZINC IN KOH SOLUTION

The passive film on a zinc electrode is often assumed to be composed of ZnO. Since removal of the electrode from the solution could alter the film composition, an in situ measurement technique is required for a qualitative analysis. We have developed a model to simulate the kinetics of anodic dissolution and passivation on the zinc electrode in alkaline electrolyte. In our model ZnO is postulated to be responsible for the passivation of the electrode. To check this hypothesis we performed photocurrent measurements and we compared the results with those obtained on bulk material. Based on the differences in photospectra as a function of electrode potential, we infer that the surface composition changes with potential. Although photospectra from the passivated electrodes are not identical to those from bulk material, key characteristics closely correspond.