Compute a Polarization Curve
We will now compute and plot a polarization curve — that is, solve for a range of cell potentials — and plot these versus the average cell current density.
Set up a Boundary Probe for the Average Cell Current Density
First introduce a boundary probe for the average cell current density at the anode gas diffusion electrode boundary.
1
In the Definitions toolbar, click  Probes and choose Boundary Probe.
2
In the Settings window for Boundary Probe, type I_avg in the Variable name text field.
3
Select Boundary 3 only.
4
In the Settings window for Boundary Probe, click Replace Expression in the upper-right corner of the Expression section. From the menu, choose Component 1 (comp1) > Hydrogen Fuel Cell > fc.nIs - Normal electrode current density - A/m².
5
Change the sign of the expression so that it reads -fc.nIs.
6
Locate the Expression section. In the Table and plot unit field, type A/cm^2.
7
Select the Description checkbox and in the associated text field, type Average cell current density.
Add an Auxiliary Sweep and Resolve
Set up an auxiliary sweep to solve for a range of cell potential values and compute the model again.
1
In the Model Builder window, under Study 1 click Step 2: Stationary.
2
In the Settings window for Stationary, click to expand the Study Extensions section.
3
Select the Auxiliary sweep checkbox.
4
Click  Add.
5
In the table, enter the following settings:
Parameter name
Parameter value list
Parameter unit
E_cell (Cell voltage)
range(1,-0.1,0.5)
V
6
In the Home toolbar, click  Compute.
Polarization Curve
A probe plot for the average current density was created by default. Modify it as follows:
1
In the Model Builder window, under Results click Probe Plot Group 3.
2
In the Label text field, type Polarization Curve.
3
In the Settings window for 1D Plot Group, locate the Plot Settings section.
4
Select the Flip the x- and y-axes checkbox.
5
Select the y-axis label checkbox.
6
In the associated text field, type Cell voltage (V).
7
In the Polarization Curve toolbar, click  Plot.