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Topic: Diffusion coefficient in cyclic voltammetry  (Read 18268 times)

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lily_m

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Diffusion coefficient in cyclic voltammetry
« on: October 26, 2010, 11:33:36 AM »
Hi all,
I was wondering if anyone might be able to help me. I have conducted an experiment in the Cyclic Voltammetry of the Ferro/Ferricyanide System. I have used different scan rates on a 1mM solution K3 Fe(CN)6 and took the voltagram readings from each of the different scan rates and plotted them on a graph (ipc vs v/s 1/2) to give a linear plot formation. From this, i must now calculate the Randles-Sevcik equation. In order to do this i must find the diffusion coefficient. I have calculated the slope and the intercept of the linear plot, can anyone please tell me how i might now calculate the diffusion coefficient from this??

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Re: Diffusion coefficient in cyclic voltammetry
« Reply #1 on: October 26, 2010, 12:19:40 PM »
from your original cyclic voltammograms you can calculate the diffusion coefficient:

peak current = 0.4463 n F A C * (n F v D / R T)1/2

n = number of electrons transfered (1 in case of forro/ferri)
F = Faraday constant
A = the electrode surface area in cm2
v = scan rate in Volt / s
R = gas constant
T = Temperature

the slope of a plot of peak current versus sqrt of the scan rate gives you (with n=1):  0.4463 F3/2 A C * (D / R T)1/2
you should know all of these variables and constants, and thus you should get D from this.

lily_m

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Re: Diffusion coefficient in cyclic voltammetry
« Reply #2 on: October 26, 2010, 12:31:18 PM »
Can't believe i missed that
Thanks a million DevaDevil, much appreciated

Borek

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Re: Diffusion coefficient in cyclic voltammetry
« Reply #3 on: October 26, 2010, 01:33:06 PM »
i must now calculate the Randles-Sevcik equation

I wonder what you meant by that.
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