Modelling of Instabilities in Coupled Electrochemical and Biochemical Reaction Systems

An electrochemical reaction followed by a chemical reaction that recovers the electroactive species in its original form is referred to as electrocatalysis. In aqueous solutions at room temperature the recovering can be achieved with the aid of an enzyme as catalysts which converts substrate S to product P. Figure 1 shows a scheme of such a system for the redox couple OX and RED. This electrochemically mediated synthesis of product P from substrate S leads to an increase of the diffusion-limited current under potentiostatic conditions due to reduction of OX. This principle is the basis of amperometric biosensors [1]. The peroxidase catalyzed reduction of hydrogen peroxide (S) with hydroquinone as H-Donor (RED) is an example. This particular system has been shown to oscillate under potentiostatic conditions [2]. Figure 2 shows three responses of this system at three different concentrations of hydrogen peroxide in the initial stock solution. Here we would like to report on attempts to explain the observed dynamic instability of the steady state current in the electrochemical reaction-diffusion system.