202
4 – Electrode reactions
D
E
2,
²>
$9
<
@
2Ș
2,
²>
$9
<
@
2Ș
, P <, Ɛ >
$@
, P <, Ɛ >
$@
Figure 78 – Graph of I
f(I
I )
m
2 2η =
− , for
(a) Pt / YSZ interface and (b) Ni / YSZ interface.
The slopes of the lines are obtained by linear regression. For platinum,
we find
2
.
RT
z F
8 28
=
from which
.
(
) .
z
96 480
8 314 860 273 8 28
=
+
#
#
.
z 0 81
=
2 and for nickel, we find
.
RT
z F
20 54
=
from which
.
(
)
.
z
96 480
8 314 860 273 20 54
=
+
#
#
z 2
=
Taking z = 1 as a first approximation, we can propose the following
mechanism for platinum:
H 2 O (g) + O
2−
surface $ 2OH
−
(ads)
V O
:: + OH
−
(ads) + e $ O
#
O + 2
1
H 2(g)
For nickel, where z = 2, we can propose
H 2 O (g) $ H 2 O (ads)
V O
:: + H 2 O (ads) + 2e $ O
#
O + H 2(g)
4 – Electrode reactions
D
E
2,
²>
$9
<
@
2Ș
2,
²>
$9
<
@
2Ș
, P <, Ɛ >
$@
, P <, Ɛ >
$@
Figure 78 – Graph of I
f(I
I )
m
2 2η =
− , for
(a) Pt / YSZ interface and (b) Ni / YSZ interface.
The slopes of the lines are obtained by linear regression. For platinum,
we find
2
.
RT
z F
8 28
=
from which
.
(
) .
z
96 480
8 314 860 273 8 28
=
+
#
#
.
z 0 81
=
2 and for nickel, we find
.
RT
z F
20 54
=
from which
.
(
)
.
z
96 480
8 314 860 273 20 54
=
+
#
#
z 2
=
Taking z = 1 as a first approximation, we can propose the following
mechanism for platinum:
H 2 O (g) + O
2−
surface $ 2OH
−
(ads)
V O
:: + OH
−
(ads) + e $ O
#
O + 2
1
H 2(g)
For nickel, where z = 2, we can propose
H 2 O (g) $ H 2 O (ads)
V O
:: + H 2 O (ads) + 2e $ O
#
O + H 2(g)