
180 Fuel Cells
rates of the reduction and oxidation processes become slow. Electrode reac-
tions of this type are termed irreversible. Intermediate behavior is generally
referred to as quasi-reversible (curve b).
In Figure 5.15, the effect of the charge transfer coefcient on the current
density and overpotential relation is shown for different values of the charge
transfer coefcient α = 0.75 (curve a), α = 0.5 (curve b), α = 0.25 (curve c), n=1,
and j
0
= 10
–6
A/cm
2
. The charge transfer coefcient represents the fraction
of additional energy that goes toward the reaction at the electrode. It is also
considered as the symmetry coefcient of ...