200
4 – Electrode reactions
i
RT
2Fi 0 η
=
(11)
c. Calculating I = i # S, we obtain
2Fi S
RT
I
0
η =
(12)
The overpotential is a linear function of current.
5. The experimentally observed linearity of the overpotential as a function of
current can be explained by the model developed in the preceding questions.
This allows us to write the expressions for exchange current:
I 0 = i 0 # S
I
2FR
RT
0
p
=
Numerical evaluation gives
.
I
2 96 480 15
8 314 1020
0 = #
#
#
.
I
m A
2 93
0 =
Solution 4.5 – Reduction of water vapor at the M / YSZ interface
with M = Pt, Ni
1. Current I as a function of cathodic overpotential η (fig. 77)
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
,>ȝ$@
,>ȝ$@
Ș>P9@
Ș>P9@
, Ɛ
, Ɛ
D
E
Figure 77 – Current as a function of cathodic overpotential at
(a) Pt electrode and (b) Ni electrode.