
255Heat and Mass Transfer in Fuel Cells
Solution to Equations 6.91 and 6.92 leads to the linear concentration distri-
bution in a gas diffusion layer given as
Cx C
a
x
ii
()
,
=+
−
s
el s
el
(6.93)
and the diffusion mass transfer rate based on Darcy’s equation is given as
jDA
C
x
DA
a
iij
i
ij
=−
d
d
el
l
. (6.94)
This solution also denes the diffusion mass transfer resistance as
R
a
ij
diff,m
el
=
. (6.95)
For the rate of reaction at the electrode–electrolyte interface where the
reactant species disappears by a rst-order reaction, the rate of mass trans-
fer rate at the surface is equal to the rate of reactant consumption and is
given as
jkAC
i
=
′′
ct