Dear Karhikeyan,

In order to calculate the diffusion coefficient you should use Levich's equation as described below. In addition, below you find two papers that describe the calculation of this coefficient.

The Levich Equation models the diffusion and solution flow conditions around a rotating disk electrode (RDE). It is named after Veniamin Grigorievich Levich who first developed an RDE as a tool for electrochemical research. It can be used to predict the current observed at an RDE, in particular, the Levich equation gives the height of the sigmoidal wave observed in rotating disk voltammetry. The sigmoidal wave height is often called the Levich current.

The Levich Equation is written as:

 IL = (0.620)nFAD2/3w1/2v-1/6C

where

IL is the Levich current (A)

n is the number of moles of electrons transferred in the half reaction (number)

F is the Faraday constant (C/mol)

A is the electrode area (cm2)

D is the diffusion coefficient (see Fick's law of diffusion) (cm2/s)

w is the angular rotation rate of the electrode (rad/s)

v is the kinematic viscosity (cm2/s)

C is the analyte concentration (mol/cm3)

Note: To use the equation as written above (with the leading 0.620), certain units must be used with the parameters listed (e.g. radians per second for angular rotation, NOT radians or revolutions per minute). If revolution (rotations) per minute (rpm) are used, a value of 0.201 should be used in place of 0.620.

While the Levich equation suffices for many purposes, improved forms based on derivations utilising more terms in the velocity expression are available.[1][2]

References

John Newman, J. Phys. Chem., 1966, 70 (4), 1327-1328

 Bard, Allen J.; Larry R. Faulkner (2000-12-18). Electrochemical Methods: Fundamentals and Applications (2 ed.). Wiley. p. 339. ISBN 0-471-04372-9.

https://en.wikipedia.org/wiki/Levich_equation

The following are two articles describing the calculation of the Difussion Coefficient of potassium ferricyanide solution:

1-The diffusion coefficient of ferricyanide ions in aqueous potassium chloride solutions with and without polyethylene oxide addition

Bruin Roffel, Jan J. Van de Graaf

J. Chem. Eng. Data, 1977, 22 (3), pp 300–302

DOI: 10.1021/je60074a004

Publication Date: July 1977

2- The Differential Diffusion Coefficient of Potassium Ferrocyanide in Dilute Aqueous Solution at 25°

Herbert S. Harned, Robert M. Hudson

J. Am. Chem. Soc., 1951, 73 (11), pp 5083–5084

DOI: 10.1021/ja01155a018

Publication Date: November 1951

Hoping this will be helpful,

Rafik

sir by using Rotating Disc electrode only use Diffusion co efficient????

for Glassy carbon electrode how to  calculate ????

Dear Karhikeyan,

Attached please find a paper that describes the calculation of a diffusion coefficient by Glassy carbon electrode.

Good luck,

Rafik

You can estimate diffusion coefficients of electrolytes using methods in the classic textbook: "Properties of liquids and gases" by Poliing, Prausnitz and O'Connell. Chapter 11 section 13 gives various methods with nice worked examples.

Please see the example for the calculation in this link; https://www.youtube.com/watch?v=TZCvoyATAuE&t=104s.