Korea Atomic Energy
Question
Asked 27th Dec, 2018
How to calculate exchange current density from Tafel plot for 2 chamber MFC? How other parameters like act potential/no of electrons are determined?
I am using potentiostat (CHI 660) to perform tafel analysis in three electrode mode, which can provide tafel slope for both electrodes and intercepts and corrosion current. There are different equations for determining (i.) exchange current density , however the simplified equation (attached) contain activation over potential or number of electrons (n). how to calculate these two parameters and exchange current density. The condition are double chamber fuel cell.
Most recent answer
overpotential = a+blog(j)
or
overpotential = (f/alpha).ln(jo)- (f/alpha).ln(j)
Popular answers (1)
Faculty of Technology and Metallurgy, University of Belgrade, Serbia
Dear Jafar,
the Tafel line is a straight line of the polarization curve in E-log(j) plot E = n+Er, where n is the overpotential and Er reversible electrode potential. So by extrapolating Tafel line to Er or n the current is exchange current, see attached graph
Gretings
5 Recommendations
All Answers (8)
Faculty of Technology and Metallurgy, University of Belgrade, Serbia
Dear Jafar,
the Tafel line is a straight line of the polarization curve in E-log(j) plot E = n+Er, where n is the overpotential and Er reversible electrode potential. So by extrapolating Tafel line to Er or n the current is exchange current, see attached graph
Gretings
5 Recommendations
Université Hassan 1er
Thank you sir Branimir N. Grgur ; Please Sir, I would like to determine I0 but I cannot find the difference between exchange current density Io and Icorr. Is Io determined from the Tafle curve and from which the Icorr is calculated or vice versa?
Faculty of Technology and Metallurgy, University of Belgrade, Serbia
Dear Ayoub,
The principle is the same, but for Io you must bave defined onlu one electrochemical reactio, for example Cu in solution contained Cu2+. If corresponding ions are not present, for example
Fe in H2SO4 than you determined Icorr. Io and Icorr have different physical meaning.
2 Recommendations
Université Hassan 1er
Thank you all for your useful responses Kafia Oulmi Branimir N. Grgur . I do not have the data. I have the following Tafel curves and polarization parameters. I want to determine the values of the exchange current density Io and limiting current density I_limit an. I'm a little bit confused, should I define them mathematically using the Bulter Volmer equation, or define them by projecting onto the curves of Tafel.
University of Batna 1
Dear Ayoub,
What is the experimental system of these results.
A combination of the anodic and cathodic Tafel equations with the mixed potential theory can, in my opinion, yield the parameters i0, ....
the following references are important
Allen J. Bard ; Larry R. Faulkner. Electrochimie ,Principes , methodes et applications 1983.
CORROSION AND CORROSION CONTROL , R. Winston Revie and Herbert H. Uhlig (2008).
Kafia OULMI
1 Recommendation
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