EIS and the Polarization Curve

Consequently, the cell voltage of a PEMFC, Ecell, can be expressed using the following equation [12] 

Erev (reversible cell potential). Erev can be expressed as 

rjint (internal loss). r]int is associated with gas crossover through the membrane. This loss equates to an internal current and remains constant even under open circuit conditions. It does not contribute to the output current or power, and decreases the electron conduction in the membrane. 

(mixed potential). As discussed in Chapter 1, the mixed potential is composed of both the cathodic 02/H20 reaction potential and the Pt/PtO anodic reaction potential. The reported mixed cathode potential is around 1.06 V (versus SHE) at standard conditions (25°C, 1.0 atm) with an 02 partial pressure dependence of 15 mV/atm [19, 20], Therefore, the value of Erev - rjint - rjmix is what we called open circuit voltage, denoted as E0cv- 

i)act (activation or kinetic loss). r)act is associated with the driving force of the electrode reaction. In practice, hydrogen and oxygen must move and attach to the surfaces of the anode and cathode in order to achieve a self-sustaining reaction. This process takes time and limits the current flow. 

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