Kinetic Model of the H2O2-SCN--OH--Cu2+ Oscillator and Its Application to the Interpretation of the Potentiometric Responses of Various Inert Electrodes Monitoring the Reaction Course

The high complexity of the kinetic mechanism of the H2O2−SCN−−OH−−Cu2+ oscillator, involving numerous intermediates, causes the oscillations monitored potentiometrically with gold or glassy carbon electrodes to exhibit opposite phases compared with the oscillations recorded with palladium or platinum electrodes. Following our previous work on the outline explanation of these phenomena, involving the concept of the mixed potential, in this paper, we present their more detailed and advanced study. For that purpose, we built up a simplified but realistic kinetic model of the studied oscillator, involving nine intermediates. Of those nine species, Cu(OH)3−, Cu(OH)2−, and HO2• were found to be crucial for the explanation of the potentiometric responses of various electrodes, under an additional assumption that the interfacial exchange current density of the HO2•/HO2− couple increases in the series GC < Au < Pt. Calculated oscillatory variations of the mixed potential for various model electrodes, compared with...