Faradaic impedance simulation of mediator-type enzyme-functional electrode

Theoretical equation of Faradaic impedance (ZF) of a mediator-type enzyme-functional electrode is derived by introducing a new theoretical model in which the diffusion of mediator and substrate, enzymatic reaction and electrode reaction are considered. The typical Faradaic impedance spectrum describes the locus of the semicircle in the Nyquist plot, due to the electric double layer capacitance and charge transfer resistance of the mediator on the electrode surface. The finite diffusion impedance is also observed whose locus shows straight line of 45° to real axis and converges on real axis in the low frequency limit. In the present paper, the behaviors of the Faradaic impedance are discussed by changing in the simulation parameters including the electrode potential, diffusion coefficients, and enzymatic reaction constant.