Nonlinear Instabilities during the Electrochemical Oxidation of Hydroxymethanesulfinate

Electrochemical oxidation of hydroxymethanesulfinate on platinum and gold electrodes was investigated in this study. Scanning electron microscopy measurements show that the electro-oxidation process caused significant pitting of Au electrodes. The continuous dissolution of the Au surface is likely to have played an important role in the sustained simple and complex oscillatory behaviors in both current density and potential observed on Au surface. On a Pt surface, only transient oscillations were observed under potentiostatic conditions, whereas sustained potential oscillations were seen under galvanostatic conditions. Electrochemical impedance spectroscopy (EIS) results indicate that the oxidation of hydroxymethanesulfinate possesses a hidden negative differential resistance, suggesting that this electrochemical oscillator belongs to the HN-NDR class. Mass spectroscopy analysis of the reaction solution suggests the formation of thiosulfate (S2O32−), bisulfate (HSO4−) as well as sulfite (SO32−).