204
4 – Electrode reactions
i 8.1 e
e
8.314 1248
0.7 2 96 480
8.314 1248
(1 0.7) 2 96 480
=
−
η
η
−
#
# #
#
# #
−
`
j
or
i 8.1 e
e
13.02
5.58
=
−
η
η
−
^
h
c. The experimental results and the theoretical curve for the anodic overpotential as a function of the logarithm of current density are shown in
figure 79.
Figure 79 – Anodic overpotential as a function of the
logarithm of current density.
The agreement between theory and experiment confirms the hypothesis
that the oxidation kinetics for hydrogen in this electrode and in these
physico-chemical conditions is limited by the charge-transfer step.
d. At high current densities, the anodic overpotential as a function of the
logarithm of current density is linear. The electrode thus follows a Tafel
relationship.
log i log i
2.3RT
n F
0
α
η
=
+
log i log 8.1 2.3 8.314 1248
0.7 2 96 480 η
=
+
#
#
#
#
log i = 0.91 + 5.66 η
ORJL>LLQP$FP
<
@
Ș>9@
ORJL
H[SHULPHQWDOSRLQWV
WKHRUHWLFDOPRGHO
4 – Electrode reactions
i 8.1 e
e
8.314 1248
0.7 2 96 480
8.314 1248
(1 0.7) 2 96 480
=
−
η
η
−
#
# #
#
# #
−
`
j
or
i 8.1 e
e
13.02
5.58
=
−
η
η
−
^
h
c. The experimental results and the theoretical curve for the anodic overpotential as a function of the logarithm of current density are shown in
figure 79.
Figure 79 – Anodic overpotential as a function of the
logarithm of current density.
The agreement between theory and experiment confirms the hypothesis
that the oxidation kinetics for hydrogen in this electrode and in these
physico-chemical conditions is limited by the charge-transfer step.
d. At high current densities, the anodic overpotential as a function of the
logarithm of current density is linear. The electrode thus follows a Tafel
relationship.
log i log i
2.3RT
n F
0
α
η
=
+
log i log 8.1 2.3 8.314 1248
0.7 2 96 480 η
=
+
#
#
#
#
log i = 0.91 + 5.66 η
ORJL>LLQP$FP
<
@
Ș>9@
ORJL
H[SHULPHQWDOSRLQWV
WKHRUHWLFDOPRGHO