
270 Fuel Cells
limiting current density is reached when the gas concentration at the electrode–
electrolyte interface becomes zero or C
i,el
= 0, and this is expressed as
jnF
C
h
a
D
i
ij
=
+
e
ch
m
el
eff
,
.
1
(6.130)
In situations where net mass transfer resistance is controlled by the diffu-
sion resistance in the electrode–gas diffusion layer only, the limiting current
density can be approximated as
jnFD
C
a
ij
i
le
eff
ch
el
=
,
. (6.131a)
In situations where net mass transfer resistance is controlled by the mass
convection resistance in the electrode–gas diffusion layer only, the limiting
current density can be approximated as
i
1
= n
e
Fh
m
C
i,ch
. (6.131b ...