198
4 – Electrode reactions
and, by neglecting the anodic overpotential,
U
E
RI 4F
RT
ln 1 I
I
th
c
Δ
Δ
=
+
−
−
,
c
m
U
0.119 0.21 7 10
4 96 480
8.314 913
ln 1 34.8 10
7.05 10
3
3
3
#
#
#
Δ =
+
−
−
−
−
−
#
#
#
^
c
h
m
U
0.125 V
Δ =
This is the value of the applied potential difference.
Solution 4.4 – Determination of exchange current
1. Figure 76 shows the electrode overpotential as a function of intensity.
We see that the curve is linear. It can be described by the following equation:
η = R p I
(1)
where the electrode polarization resistance R p = 15 Ω.
<
<
<
<
<
,>P$@
Ș>P9@
Figure 76 – Electrode overpotential as a function of intensity.
2. a. 2 At the (La 0.8 Sr 0.2 MnO 3−δ -YSZ) / YSZ interface, the oxygen adsorptiondesorption reaction is expressed as
O 2 + 2s m 2O-s
(a)
where s denotes an adsorption site.
The corresponding reaction rate under the conditions given in the
problem statement is
4 – Electrode reactions
and, by neglecting the anodic overpotential,
U
E
RI 4F
RT
ln 1 I
I
th
c
Δ
Δ
=
+
−
−
,
c
m
U
0.119 0.21 7 10
4 96 480
8.314 913
ln 1 34.8 10
7.05 10
3
3
3
#
#
#
Δ =
+
−
−
−
−
−
#
#
#
^
c
h
m
U
0.125 V
Δ =
This is the value of the applied potential difference.
Solution 4.4 – Determination of exchange current
1. Figure 76 shows the electrode overpotential as a function of intensity.
We see that the curve is linear. It can be described by the following equation:
η = R p I
(1)
where the electrode polarization resistance R p = 15 Ω.
<
<
<
<
<
,>P$@
Ș>P9@
Figure 76 – Electrode overpotential as a function of intensity.
2. a. 2 At the (La 0.8 Sr 0.2 MnO 3−δ -YSZ) / YSZ interface, the oxygen adsorptiondesorption reaction is expressed as
O 2 + 2s m 2O-s
(a)
where s denotes an adsorption site.
The corresponding reaction rate under the conditions given in the
problem statement is