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2D-Cyclic Voltammetry Model: 1 electron 2 speicies dillute diffusion

Robert Palumbo, Valparaiso University
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A simple COMSOL mph cyclic voltammetry (CV) 2D time-dependent model was developed. The model presumes the electrode kinetics are described by a 1 electron transfer process. The transport of a reduced and an oxidized species is described by time-dependent mass transfer principles for diffusion under dilute conditions.

The model is that of a two electrode cell. The reaction at the working electrode is described by concentration dependent Butler-Volmer kinetics. The counter electroded is modeled so that it behaves like an ideal reference electrode.

As in an experimental CV study, the applied cell voltage sets the potential of the working electrode with respect to the reference electrode, in our case also the counter electrode. In the model, the potential of the counter electrode is set to that of the electrolyte at the electrode surface and that potential with respect to ground is set to zero. There is very little potential drop between electrodes in the electrolyte. There is no current flow in the counter electrode. Thus all of the cell's response to an applied potential is the result of changes between the working electrode and the electrolyte next to its active surface, exactly the outcome one looks for in selecting a reference electrode for CV studies.

The model is seen as a tool to help one interpret experimental voltammograms. In this regard, it must also be seen as template for building models with more complex electrochemistry conditions, e.g., multiple electron transfer processes, with chemical reactions and more complex mass transfer conditions. One can then form an hypothesis regarding the interpretation of an experimentally obtained CV, The COMSOL simulations will either bolster ones support for the interpretation or be proof that one needs a better hypothesis.

User Comments

goldfronts
Sep 9, 2012 at 3:07pm UTC

Can't open this file in COMSOL 4.1? Any suggestions as the progress windows just hangs up.

Thanks

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