
170 Fuel Cells
The rate constants for the forward and backward reactions, k
f
, k
b
, can then
be modied to
k
kT
e
G
RT
f
B
=
−
→
∆
(5.29)
and
k
kT
e
G
RT
b
B
=
−
→
∆
(5.30)
for a reaction that occurs in n-steps with the gth step being the rate-controlling
step.
As mentioned earlier on the energetic reactions, the reactions rates can be
modied by changing the potential difference across the electrode and the
electrolyte. Consider the electron transfer reaction
Ox
ed.
Red
Ox
+−
+ n
k
k
(5.31)
The rate constants k
Ox
and k
Red
can be inuenced by the applied voltage
according to the transition state theory from chemical kinetics. When a
potential is applied to ...