Plot
overpotential Vs. Log(|J/mA-cm-2|)
Take the data range near to the onset.
from plotting (V) vs. log( i ) then the slope of straight line equation is the Coefficient of X
you can send me the Microsoft Excel file including V and log i
Hi,
1. I believe you are not using SHE or RHE electrode, rather you are more likely using Ag/AgCl electrode. You need to convert the potential to SHE or RHE in the first step. For instance, my Ag/AgCl electrode is filled with 3M of KCl solution, the conversion is:
VSHE = Vobtained + 0.21V. (Check literature for detail)
2. Secondly, due to the series resistance arises from instrumental cables and electrolyte etc. , you have to consider the iR drop (which can be obtained from Nyquist plot at high frequency). Hence the actual potential that drives the HER will be:
Vactual = Vobtained + 0.21V - iR
3. The geometrical current density is:
j = i x 1000/A (mA/cm2)
4. Since you are using excel, I suggest the following syntax:
Vactual = Vobtained + 0.21 + ABS(i)*R
log(j) = log(ABS(j))
5. Plot Vactual vs. log(j). Find the gradient of Vactualvs. log(j) in linear region, do linear fitting, it is the Tafel slope.
You need to do more literature review, especially in the "Experiment section" or "Methods" . Do not always choose journals with high impact, they assume you know the technical knowledge very well.
Cheers,
Shu Hearn
Your data seems weird to me. First of all, what material are you using? Is your system deaerated? About the Excel data, are the values of current in correct unity? Because when I looked E vs log(j) plot seems to be sort a oxygen limiting current, but the value doesn't correspond to this reaction. Besides that Tafel slope for HER obtained by your date shows a value of 1.187 V per decade, this value is extremely high, for exemple, HER on Pt or Pd shows a slope around 120 mV per decade. It means the reaction onto your material is highly unfavorable. In addition, if the values are strictly correct and if your system is aerated, the oxygen reaction developed an extremely high current density, this influences all cathodic curve. This should be considered if you are calculating HER kinetic.
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