On the Development of a General Electrochemical Impedance Model

A general model and computer code have been developed for writing down by inspection the impedance of one-dimensional systems involving arbitrary numbers of coupled electrochemical and chemical processes under activation or mass transport control. This code is based on the direct solution of the mass transport equations by using the finite difference up-wind scheme. The current version of the code is able to handle any arbitrary number (and complexity) of homogeneous and heterogeneous reactions. This code simulates, and can be used for optimization on, coupled chemical/electrochemical reaction mechanisms at rotating disk electrode or by using the Nernst diffusion layer approximation. The model can be readily optimized on experimental EIS data, in order to determine values for various model parameters (rate constants, transfer coefficients, diffusivities, etc). The application of the code is illustrated with "synthetic" EIS data and with some experimental data obtained on a rotating disk electrode.