Hi,

Have a look at classical textbook such as Bard and Faulkner or

https://www.bio-logic.net/wp-content/uploads/20131128-Application_note_41-1.pdf

https://www.bio-logic.net/wp-content/uploads/20131128-Application_note_41-2.pdf

Hope this helps.

jpd

Hi Hong,

You record the CV at a fixed scan rate, you don't need to change it (the most common is 50 or 100 mV/s)but you can see the effect of the scan rate recording CVs at different scan rates. Two main reasons: i) effect on the intensity of the peak current: to see if the redox process is controlled by diffusion or adsorption (if the peak current is proportional to square root of the scan rate the process can be considered diffusion-controlled; if it is proportional to the scan rate (linearly), then it is adsorption-controlled). ii) effect on the potential: to see if the process is reversible or irreversible (fast or slow electron transfer). In reversible processes the potential does not change with peak current.

Then, you can look at the peak current (related to mass transport phenomena) or the potential (related to electron transfer).

Good luck,

Dear Hong,

I Completely agree with M.Teresa Fernández-Abedul . Varying the scan could help us to understand the nature of the reaction (reversible or quasi-reversible). In a reversible reaction is peak potential and peak current are independent of scan rate. Diffusion coefficient can be understood based on the the linear relationship of the current vs scan rate or Current vs square root of scan rate. Electrochemical active surface area can be measured based on the Randles–Sevcik equation. For details please follow the book Instrumental methods in Electrochemistry by Professor D. Pletcher, Southampton

University and Electrochemical methods by Bard and Faulkner

I definitely agree with the answer of M. Teresa.

I am measuring the antioxidant activity of one plant by CV. We know that the limiting stage is diffusion, then how can we use this information for an antioxidant?

the easy answer to this is concentration time current volts are connected in cyclic voltammetry as randles sevcik eq lower volts per second lower the current in low concentration so peak will we lower so u need to set everything as such u get good reduction or oxidation peak at optimum conc. at lower scan rate and as amount of oxi redu species will change and the at minimum potential window the less volts be needed to electro reduce or electro oxidise a species and at what optimized value of scan rate, nd even as less cocentration u will get more peak current.