Electroanalysis
Start defining the physics by setting the diffusion coefficients for the two species of the redox couple.
Electrolyte 1
1
In the Model Builder window, under Component 1 > Electroanalysis, Click Electrolyte 1 . The ‘D’ in the upper left corner of a node means it is a default node.
2
Locate the Diffusion section in the settings window.
3
In the DcA and DcB text fields, type DA and DB, respectively.
Concentration 1
Set the concentration at the right boundary to bulk concentration.
1
In the Physics toolbar, click Boundaries  and choose Concentration  .
2
Select Boundary 2 only.
3
In the Concentration section of the Concentration Settings window, select the Species cA and Species cB checkboxes.
4
In the c0,cA text field, type c_bulk.
Electrode Surface 1
Set up the electrode surface and the cyclic voltammetry settings on the left boundary.
1
In the Physics toolbar, click Boundaries  and click Electrode Surface  .
2
Select Boundary 1 only.
3
In the Electrode Phase Potential Condition section of the Electrode Surface Settings window, choose Cyclic voltammetry from the list.
4
In the Linear sweep rate, type v.
5
The voltage will be cycled between the vertex potentials. When the start potential is not specified, the sweep will start at Vertex potential 2. Enter the following:
- E_vertex1, in the Vertex potential 1 text field.
- E_vertex2, in the Vertex potential 2 text field.
Electrode Reaction 1
Specify the electrode reaction as a Butler–Volmer reaction, which is concentration dependent as defined by the stoichiometric coefficients in the reaction.
1
In the Model Builder window, expand the Electrode Surface 1 node and click Electrode Reaction 1.
2
In the settings window for Electrode Reaction 1, locate the Stoichiometric Coefficients section.
3
In the νcA and νcB text fields, type 1 and -1, respectively.
4
Locate the Electrode Kinetics section and type in i0ref in the i0,ref(T) field.
Double-Layer Capacitance
1
In the Model Builder window, right-click Electrode Surface 1 and choose the boundary condition Double-Layer Capacitance.
2
Click the Double-Layer Capacitance node and type Cdl in the Cdl text field.
Initial Values 1
Continue with specifying the initial concentration values. This will set the concentration values when the simulation starts at t=0.
1
In the Model Builder window under Component 1 > Electroanalysis (tcd), click Initial Values 1 .
2
In the Settings window for Initial Values, locate the Initial Values section.
3
In the cA text field, type c_bulk-cB0*(1-x/L).
4
In the cB text field, type cB0*(1-x/L).
The node sequence in the Model Builder under the Electroanalysis interface should match this figure: