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Files:
Scan rate CV interactive .EXP
Scan rate CV interactive 1I.CRV
Abstract
Platinum (Pt) is known as an "inert" metal with
a strong catalytic activity for many electrochemical reactions.
Many components can be adsorbed on Pt surfaces and the adsorption
of hydrogen is a well known phenomenon in electrochemistry. This
experiment concerns two fundamental mechanisms which occur on a
Pt electrode polarised in a strong acid media, H2SO4.
*Cathodic area: Hydrogen adsorption / desorption (from - 250 mV
to + 200 mV versus Calomel)
*Anodic area: Platinum oxides formation and reduction (from + 200
mV to 1300 mV versus Calomel).
The CV interactive enables you to modify the scan rate during the
experiment. Each time you modify this scan rate the potential is
hold for a short time, the circuit is not opened. A cyclic voltammetry
is a dynamic equilibrium and the modification of the scan rate disturbs
the interface. This is why the change is performed during the scan
in the anodic direction in the potential area where the current
is minimum. This extract from the original CV interactive establishes
the correlation between the scan rate and the peak amplitudes. The
higher the scan rate, the bigger the peaks.
Sample
Solution H2SO4 0.5 M
WORK Platinised platinum [2]
Plate ± 5X5 mm
(CDC641T conductivity cell)
REF Calomel electrode (XR100)
AUX Platinum wire (XM100)
CP06 cell at ambient temperature (22°C) without degassing with Nitrogen.
Settings - Experimental
A Chrono Amperometry starts the sequence.
It polarises the WORK at -300 mV /REF to stabilise the WORK interface
and to saturate the solution with H2 in the vicinity of the WORK
interface. Scan rate 30, 80, 130 & 250 mV/s.
Curve examination
1) Display:
Type = Normal X = Potential Y1 = Current Y2 = No
The peak magnitude and the peak position
depends upon the scan rate
2) Display:
Type = Normal X = Time Y1 = Current Y2 = Potential
The scan rate has been adjusted during
the experiment.
Conclusion
The CV interactive establishes that the peak
magnitude and the peak position are correlated with the scan rate.
References and notes
[1] P.A.
Christensen and A. Hamnett "Techniques and Mechanisms in Electrochemistry",
p228 Blackie A&P (Imprint of Chapman&Hall, Glasgow, 1994
[2] Platinised
platinum amplifies the catalytic effect of Pt.
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