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Topic: Why does current change direction in cyclic voltammetry?  (Read 2612 times)

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Offline LogicX

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Why does current change direction in cyclic voltammetry?
« on: October 10, 2012, 07:37:05 PM »
You start at a certain voltage. Then you decrease this voltage to be more negative which reduces the analyte. Then you switch at a set voltage and increase the potential so that it is becoming more positive. Why does this switch the direction of the current so that on the reverse sweep the species is oxidized?

At the same magnitude current on the forward and reverse sweeps the species is either getting reduced or oxidized, respectively. I would have initially thought that because the voltage is the same at this point on the reverse scan, when you reach that voltage again you would simply continue to reduce the product more. But instead the flow of electrons reverses; why?

The difference is not in the magnitude of voltage but the direction of the sweep. How can this matter? Isn't a certain negative voltage still the same negative voltage regardless of which direction you are sweeping"? Shouldn't the current flow in the direction based on the sign of the voltage, not the direction of the sweep?

I'm fundamentally confused about this process.

Offline Hunter2

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Re: Why does current change direction in cyclic voltammetry?
« Reply #1 on: October 11, 2012, 01:04:25 AM »
Its the rectifier who does the work. You run a certain time positive. Then the polarity of the outlet is changed, like you put the cables out and connect them in the opposite way.

Offline Borek

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Re: Why does current change direction in cyclic voltammetry?
« Reply #2 on: October 11, 2012, 04:19:44 AM »
Its the rectifier who does the work. You run a certain time positive. Then the polarity of the outlet is changed, like you put the cables out and connect them in the opposite way.

Not only it is wrong, it is also completely unrelated to the question.

I would have initially thought that because the voltage is the same at this point on the reverse scan, when you reach that voltage again you would simply continue to reduce the product more. But instead the flow of electrons reverses; why?

Hint: what you wrote would be true if you were vigorously mixing the solution during the experiment.
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