
190 Fuel Cells
η
c
c
=−
j
j
RT
nF
0
.
(5.110)
For the fuel cell, the overpotential on the anode is positive; this makes the
rst term on the right-hand side of the anode current density equation
(Equation 5.103) negligible compared to the second term for moderate values
of overpotential. Thus, the anode current density is reduced to
jje
T
=−
0a
Ox,a a
αη/
.
(5.111)
Thus, at anode, oxidation current is dominant. The negative sign indicates
net oxidation wherein the electrons are leaving the electrode. For cathode,
the overpotential is negative; hence, the second term on the right-hand side
of the cathode current density equation (Equation 5.108) is negligible ...