I have seen that occasionally CV curves are not a connected cycle, instead there is a difference at the starting to end point. Why does it sometimes occur?
Nipa Roy this depends on several factors. When recording a CV voltammogram the sweep parameters can be adjusted, such as initial and final potential, as well as with respect to which potential the working electrode potential is measured. On this basis it can happen:
1. that intentionally the initial potential is set different from the final potential depending on which processes you want to study.
2. That the reference potential is assumed to be the OCP, in which case, sometimes the OCP changes over time, causing the initial potential measured to not match the final potential. This is solved by recording the CVs at a sufficient time for the OCP to be stable over time.
3. Another possibility, less likely, is that if the sweep potential is measured against the reference electrode, a polarization of the reference electrode may occur so that the initial potential does not match the final potential because the reference changed. But this is unlikely in a common modern voltammetric experiment, because the currents are low. But since it is possible, it is not ruled out. It should be noted that this is an experimental error.
I hope it helps. Regards!
I think that what you are seeing is the difference between a CV that is the first scan only and a CV that is not the first scan. In the first scan, the initial current is at the baseline (ideally) and the end current will be below the baseline.
See figure 7 in this paper for a good example:
https://pubs.rsc.org/en/content/articlehtml/2014/fd/c4fd00034j
However, if there is no delay between the next and subsequent scans, the current will start at the same value as the end of the first scan. Now the current at the beginning and end are all connected. See Figure 4 in this paper for an example
Article Single Microfluidic Electrochemical Sensor System for Simult...
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