Models 2450-EC, 2460-EC, and 2461-EC Potentiostats And Galvanostats User's Manual
Section 2: Cyclic Voltammetry
077110402/November 2016
2-17
The voltage peaks in the waveform are the anodic (E
pa
) and the cathodic (E
pc
) peak potentials.
Figure 38: Example voltammogram generated by a 2450-EC
In this example, the scan begins at E1 and the potential becomes more positive, causing the anodic
current (to rise rapidly and peak at the anodic peak potential (E
pa
).
At E2, the scan direction switches to negative for the reverse scan. As the current becomes more
negative, cathodic current flows as the electrode process is reduced. A cathodic peak potential
occurs at E
pc
.
At E3, the direction reverses again and the voltage is swept until it reaches E4. From the potential
sweep, important information about the experiment can be derived and analyzed.
Keithley galvanostat scan theory
The 2450-EC, 2460-EC, and 2461-EC digital potentiostats do not output a truly linear voltage; they
output very small, digitized steps from 0.1 mV to 10 mV for a specified time (dt), depending upon the
scan rate. See the next figure. While this will not cause significant errors in normal geometry cells
(such as 10 mL analytic and most galvanic cells), there might be errors when using micro and
ultramicro electrodes. The voltage step sizes used are calculated during scanning based on the user
set scan rate:
•
100 μV (0.1 mV per second ≤ scan rate < 35 mV per second)
•
1 mV (35 mV per second ≤ scan rate < 350 mV per second)
•
10 mV (350 mV per second ≤ scan rate ≤ 3500 mV per second)
Figure 39: Potential scan
