Performance Characteristics of a Fuel Cell

F -F Pact,cathode,ORR Pact,anode,HOR f ohmic Pconc,anode 

The rational design of improved electrocatalyst materials requires first and foremost a fundamental understanding of the origin of the kinetic overpotential. Over 

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Figure 3.3.7 Theoretical (dashed dotted) and real (solid) cell voltage (V) - current density (I) performance characteristics of a fuel cell. Overpotentials are responsible for the difference between theoretical and real performance and cause efficiency losses. They split into (i) activation polarization overpotentials at anode and cathode due to slow chemical kinetics, (ii) ohmic polarization overpotential due to ohmic voltage losses along the circuit, and (iii) concentration polarization overpotentials due to mass-transport limitations. The activation overpotentials of the cathode are typically the largest contribution to the total overvoltage.

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