Fuel cell diagnostics polarization curve

Figure 1.27. A sample fuel cell polarization curve obtained from the diagnostic modeling PEM fuel cell with an active area of 192 cm, designed by NRC-IFCI...

Nevertheless, quantification of losses on the basis of a polarization curve is difficult because contributions from the different underlying processes overlap. Consequently, other electrochemical methods are needed to be carried out for an exhaustive fuel cell behavior diagnostic. 

In Chapter 1, Figure 1.4 shows a typical polarization curve of a PEM fuel cell. The voltage loss of a cell is determined by its OCV, electrode kinetics, ohmic resistance (dominated by the membrane resistance), and mass transfer property. In experiments, the OCV can be measured directly. If the ohmic resistance (Rm). kinetic resistance (Rt, also known as charge transfer resistance), and mass transfer resistance (Rmt) are known, the fuel cell performance is easily simulated. As described in Chapter 3, electrochemical impedance spectroscopy (EIS) has been introduced as a powerfiil diagnostic technique to obtain these resistances. By using the equivalent circuit shown in Figure 3.3, Rm, Rt, and R t can be simulated based on EIS data. 

Polarization curve is the most important characteristic of a fuel cell. It may be used for diagnostic purposes, as well as for sizing and control of a fuel cell. In addition to potential-current relationship, other information about the fuel cell may also become available just by rearranging the potential-current data. 

---