Modelling - Mediator Oxidation

Mediator Oxidation

In a third electrochemical reaction the reduced mediator is regenerated at the electrode.This electrochemical oxidation at the anode surface occurs as shown in equation:

,where M_red is the reduced mediator and

               Mox the oxidized mediator.

Then the current output can be calculated based on formula according to the Faraday's law:

,where I is the current density [A]
[M_red] is the concentration of reduced mediator in the chamber
n is the number of electrons taking part in the electrode reaction,
F is the Faradays constant (96 500 C) and
k₃ is the reaction rate, mentioned above.

Simulation

The values k₃ obtained as mentioned above waas applied in the simulation of the current output in the final reaction of the three-reaction model. The start concentrations of the NAD⁺ and oxidized mediator were set as in the simulations preformed for the proceeding reactions at 100 µM. The simulation time span was set for 60 sec. The resulting plot for the mediator MB is shown in the figure1 below:

Figure 1: Curves for the current output, fluxes of concentration of the intermediates. Simulation performed for the start concentration of both NAD⁺ and oxidized mediator at 100 µM.

Further simulation has been performed for four different start concentrations of the oxidised mediator in order to investigate how varying start concentration influence the current output. The concentrations were set at 10 µM, 50 µM, 100 µM and 500 µM. The time span was set at 30 sec.

The MATLAB source code for both simulations can be obtained here and here.

Analogous simulations have been performed for the mediator NMP. As the reaction rate k₃ specific of the could not be accessed, the value specific for the mediator MB was applied. The according .m files with MATLAB source code can be downloaded from here and here.

References