Dynamic Behaviour of Pt Microelectrode Arrays during the Galvanostatic Oxidation of CO

The electroxidation of carbon monoxide has been used as a prototype reaction in fundamental electrocatalysis¹. On Pt electrodes, the CO bulk electroxidation is a typical example of a bistable electrochemical system². The bistable kinetics of the reaction stems from the interplay between the competitive Langmuir-Hinshelwood mechanism and the controlled mass transport of CO toward the electrode. On macroscopic Pt electrodes, different kinds of spatio-temporal instabilities may occur during the CO oxidation depending on the nature and the strength of coupling existing between different parts of the electrochemical system^3,4.

            In this presentation we will discuss the influence of the size, the interelectrode distance and  the supporting electrolyte concentration on the dynamic behaviour of a Pt microelectrode array in the electrooxidation of saturated CO solutions. A custom built galvanostat allows the individual currents flowing through each of the microelectrodes to be measured. Three different kinds of cooperative behaviour could be evidenced for the first time and explained with the help of mathematical modelling. When the applied reaction current value is linearly increased, sequential activation of the microelectrodes was observed (cf. Fig.), while a complex dynamical switching regime was obtained when the current was kept constant⁵. At low supporting electrolyte concentration, spontaneous oscillations of the potential emerged through the coupling of individual electrodes.

Acknowledgements: Financial support from the International Center for Frontier Research in Chemistry (University of Strasbourg) and of the Labex “Chemistry of Complex Systems” is gratefully acknowledged

 

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