Chemistry Reference
In-Depth Information
6
4
5
3
4
2
3
1
2
1
0
1.0
1.2
1.4
1.6
1.8
2.0
2.2
Log
d
(mm)
9.14
Logarithmic plot of the impedance at zero phase-angle shift as a
function of distance between the electrode (
d
) obtained from the
electrochemical cell with palladium and textile electrodes,
A
=
490.6 mm
2
,
T
=
298.0 K and an electrolyte concentration of (1)
1
¥
10
-
1
, (2) 1
¥
10
-
2
, (3) 1
¥
10
-
3
and (4) 1
¥
10
-
4
mol l
-
1
.
the defined conditions of
d
min
are valid only for the three investigated struc-
tures because of its dependency on the surface roughness. The cause of this
effect can be explained easily using Fig. 9.11b. The roughness of textile elec-
trodes has an influence on the measured impedance because of small dif-
ferences between
Z
1
,
Z
2
, to
Z
n
. However, these differences should be related
to the distance between the electrodes because the roughness introduces
locally different distances between the electrodes.
The smaller the geometrical distance between the electrodes, the more
important the local differences in distance become, which causes a drift
away from linearity for the relationship between log
Z
and log
d
. In addi-
tion, from the experimental data, it could be seen that this drift is slightly
more expressed for the non-woven structure, which is in fact the structure
with the roughest surface. From additional experiments, it was found that
Equations 9.5-9.7, obtained with the palladium electrodes, are also valid for
the textile electrodes on the condition that
d
min
> 40 mm and
A
min
> 75 mm
2
.
From the data introduced in Figs 9.10, 9.13 and 9.14, values for
k
1
,
k
2
and
k
3
can be calculated and are presented in Tables 9.5, 9.6, 9.7 and 9.8. It can
be seen that the values for the textile electrodes are slightly higher com-
pared with those obtained in section 9.2. However, comparison of the data
obtained in this chapter for palladium and textile electrodes did not reveal
