STATIONARY AND NONSTATIONARY ELECTROCHEMICAL RESPONSE OF POLYCRYSTALLINE INDIUM IN ALKALINE MEDIA

Stationary and non-stationary responses of polycrystalline indium electrodes in NaOH (0.05-4 M) solution at 25°C were studied. Anodically formed films, their kinetics and chemical stability were discussed as a function of potential domain, time diffusing process, and hydroxide concentration. These processes were investigated through potentiostatic polarisation conventional voltammetry and potentiostatic transients techniques. SEM observations were also applied. The overall anodic reaction can be interpreted through a model comprising a number of parallel reactions following the initial formation of In(OH)ad species at the electrode surface level. The relative contribution of each parallel reaction is determined by the concentration of OH- ion at the interface. The anodic behaviour of indium appears to be under a mixed control, a surface reaction plus a diffusion process. On increasing pH, the control process becomes the OH- ion diffusion through the anodic film. © 1990.