Chemistry Reference
In-Depth Information
1.8
1.6
y
= 0.4854x + 0.2552
R
2
= 0.9972
4
1.4
3
1.2
y
= 0.5077x + 0.1728
R
2
= 0.9992
2
1.0
0.8
y
= 0.9559x - 1.4925
R
2
= 0.9986
y
= 1.0503x - 1.4695
R
2
= 0.9827
0.6
1
0.4
0.2
0
1.5
1.7
1.9
2.1
2.3
2.5
2.7
2.9
Log
v
(mV s
-1
)
7.3
Logarithmic plot of the peak current observed in the curves in
Fig. 7.2 as a function of scan rate. Curve (1) peak I
c
, (2) peak III
a
,
(3) peak III
c
and (4) peak IV
c
. (Reprinted from
Journal of
Electroanalytical Chemistry
, Vol 567 No 2, De Wael et al, 'Study of
the deposition of . . .', pp 167-73 (2004), with permission from
Elsevier.)
Co(II)TSPc. Figure 7.3 shows the relationship for some peak currents
observed in Fig. 7.2.
7.2.3
Concentration study
The experiments described in section 7.2.1 were repeated for other
Co(II)TSPc concentrations, and qualitatively similar results were obtained.
The same peaks were observed and they also appeared/disappeared as a
function of scan number, but the number corresponding with the break in
the trend of the behaviour depends on Co(II)TSPc concentration. Figure
7.4 shows the scan number as a function of Co(II)TSPc concentration where
the peaks do not increase further with continued scanning and where new
peaks appear while existing peaks disappear. These results indicate clearly
that Co(II)TSPc is electrodeposited at the electrode surface and the time
(or scan number) needed to obtain maximum coverage is dependent on the
Co(II)TSPc concentration in solution. This is expected because more
Co(II)TSPc in solution means more of it is transported towards the elec-
trode surface per time unit. The fact that the charges of the peaks II
a
, III
a
,
I
c
and II
c
at the scan number of maximum coverage are not dependent on
Co(II)TSPc concentration shows that the electrodeposition is controlled by
kinetics. The fact that at the scan number of maximum coverage, the other
