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I'm in an instrumentation course and we covered cyclic voltammetry earlier in the semester and will be doing an experiment in CV next week.

My question is this:

If you have a reaction and sweep the potential, will the new peaks be entirely within the previous peak? (Meaning: lower magnitude in the subsequent peaks?) It seems that with each sweep, it should have lower electrical potential.

Or would the peaks trace over the previous ones, nicely?

Pardon me for not fully understanding (or if my question is wrong.)

Enjoy a poorly drawn image of what I mean:

enter image description here

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Perhaps your observation is an indication of irreversible reaction conditions. More specifically, a tight deposit on the electrodes hampering the advancement of the electrochemical reactions. This happens sometimes with some less soluble organic dyes used organic electronics, too. Take a look if the electrodes are still shiny, maybe they need to be cleaned again. If this is the case, try out a different solvent/electrolyte system.

One aiding companion to trouble shoot is this.

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The oxidation and reduction peaks on the cyclic voltammogram should be reproducible if done under the same conditions and for a reversible reaction, i.e. no side reactions depleting species. The difference in voltage between the peaks can be used as a test of reversibility. Most probably as @Buttonwood writes you have an irreversible reaction where the peak shapes are not the same in shape or size as time progresses due to various other species being formed. Sometimes, such as with quinones, it is possible to prepare an electrode so that it can behave reversibly.

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