AN INSITU SPECTROSCOPIC STUDY OF THE ANODIC OXIDE FILM ON A COBALT ELECTRODE AT PH 4-14 BY POTENTIAL-MODULATED REFLECTANCE

The anodic oxide film on a Co electrode has been studied by UV-visible potential-modulated reflectance (PMR) over a wide range of pHs (4-14) and polarization potentials. PMR is a very sensitive in-situ technique, but the interpretation of the PMR spectra of anodic oxide films is not complete. Here we follow the criterion that the PMR maxima of the films correspond to optical absorption edges of compounds present in them. According to the PMR results, the film composition is similar in both weakly (pH 9.2) and strongly (pH 13-14) alkaline media. Only some of the observed PMR maxima could be assigned, owing to the lack of spectroscopic data of Co bulk oxides, but additional conclusions were obtained by comparing PMR and voltammetric results. © 1990.