A new oscillatory mechanism for the electro-oxidation of iodide involving two phase transitions and a disproportional reaction

Oscillations have been first observed during iodide oxidation in alkaline solution on a static platinum electrode, where phase transitions at the interface of electrode/solution are essential. The film formation of solid iodine acts as a negative nonlinear feedback slowing down the iodide oxidation due to its poor conductivity, and oxygen evolution as a positive nonlinear feedback by destroying the iodine film mechanically and by promoting its dissolution through convection mainly via a disproportional reaction. Based on the results of electrochemical experiments and in situ Raman spectroscopy, a tentative mechanism is given concerning the interfacial phase transitions and the disproportional reaction.