287Charge and Water Transport in Fuel Cells
For the negligible effect of reaction rates on the concentrations of the reac-
tant and product at the electrode, that is, assuming C
R
≈ C
R,o
and C
P
≈ C
P,o
, the
equation reduces to
jjee
i
nF RT nF RT
ii iii
−−
o
eact eact
,
/( )(
(
,, ,
αη αη
)
(7.19b)
For anode and cathode electrodes, Equation 7.19b can be written as
Anode:
nF RT nF RT
aa act,
aact,a
/( )(
1
(7.20a)
Cathode:
jjee
nF RT nF RT
cc act,
cact,c
/( )(
1
. (7.20b)
7.1.2.2 Boundary Conditions for Electrical Potential
In the solution of electrical potential equations for the electrode gas diffusion
layer, the active layer is considered as the boundary and the charge transfer
current densities given by Bu ...