eDAQ Picostat, User Manual

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eDAQ Potentiostats 109
A P P E N D I X D
D
Electrochemical
Equations
Linear Sweep and Cyclic
Voltammetry
The Randles-Sevcik Equation
For a substrate with a reversible redox reaction, at a planar disk
electrode, in an unstirred solution, the peak current during linear
sweep, or cyclic voltammetry, is given by the Randles–Sevcik equation:
The potential where this occurs is given by:
where
= current peak during anodic scan (A)
= current peak during cathodic scan (A)
= potential at current peak for anodic scan (V)
= potential at current peak for cathodic scan (V)
= half potential as determined by cyclic voltammetry (V)
n = the number of electrons transferred to (or from) the substrate
molecule
A = area of the exposed surface of the electrode (cm
2
)
for an oxidation (anodic scan)
for a reduction (cathodic scan)
i
pa
269 n
3 2
⁄
AD
1 2
⁄
C
ν
1 2
⁄
=
i
pc
269
–
n
3 2
⁄
AD
1 2
⁄
C
ν
1 2
⁄
=
E
pa
E
1 2
⁄
0.0285
n
------------------------------ + = E
pc
E
1 2
⁄
0.0285
n
------------------------------ –
=
i
pa
i
pc
E
pa
E
pc
E
1 2
⁄