ELECTROCHEMICAL-BEHAVIOR OF CHROMIUM(III)-HEXACYANOFERRATE FILM-MODIFIED ELECTRODES - VOLTAMMETRIC AND ELECTROCHEMICAL IMPEDANCE STUDIES

Chromium(III)-hexacyanoferrate (CrHCF) films on wax impregnated graphite electrodes have been studied by voltammetry and electrochemical impedance spectroscopy. When a CrHCF film is transferred from HCI to another electrolyte solution a ''break-in'' effect is observed during continuous potential cycling past the formal potential of the film. Cyclic voltammetry shows a single electron transfer reaction, and the voltammetric behavior of the electrode can be interpreted in terms of the insertion electrode concept. The ion effect of the supporting electrolyte indicates that the ion permeability of the film is mainly determined by the radius of the hydrated cation. Electrochemical impedance results suggest that the electrode reaction of the film is mainly controlled by the transport of counter-ions. The electrochemical impedance spectra of the original film and the ''broken-in'' film reveal that the large limiting current of the original film in HCI solution is caused by the catalytic evolution of oxygen, rather than by a capacitive current.