Complex Dynamic Behavior During the Electro-Reduction of Bromate Ions

Abstract

This article describes the electrochemical reduction of bromate ions in strongly alkaline media on platinum electrodes. Bromates’ importance stems from its wide use in a variety of industrial processes, its incorporation into energy storage devices, as well as its known toxicity, which has led to it being designated as a human carcinogen. Interestingly, during the electro-reduction of bromate in alkaline solutions sustained oscillatory behavior was observed in both current and potential under both potentiostatic and galvanostatic control. Mechanistic characterization using electrochemical impedance spectroscopy (EIS) lead to the discovery that the oscillatory behavior is driven by the presence of a negative differential resistance (NDR). The EIS measurements allowed for the classification of the bromate oscillator into the HN-NDR class, which was supported by potentiostatic oscillations emerging once sufficient external resistance was included into the system as well as oscillating under galvanostatic conditions. Through a systematic exploration of experimental conditions, the electrochemical bromate oscillator also displayed complexity in the form of mixed-mode oscillations as well as complex bursting patterns.