- I converted E(V) into E vs RHE and then calculated the value of overpotential.
- I converted the current (A) to the current density (mA/cm2) and took the logarithmic value.
- I took the log J value along the x-axis and overpotential (V) along the y-axis.
- Now I need Tafel value in the form of mV/dec.
Dear Karthikeyan,
First of all, from the j-V polarization curve, take the data from the region where the current just starts to increase (you can roughly take 100-150 mV from the onset). Now, convert E to η (V vs RHE) and j to log j (mA cm-2). Now plot, the graph should have x-axis as log j (mA cm-2) and y-axis as η (V vs RHE), you will get a trace on plotting. The slope of the linear region of this trace is Tafel slope (in V/dec). I hope that answers your question.
1. You are taking the whole voltage range for Tafel analysis. You may restrict your range as I mentioned in my previous response.
2. If the y-axis units are in Volts then you may multiply the as-obtained slope by 1000 to have Tafel slope units in mV/dec.
Also, Tafel slope value can be more than 100 mV also (For e.g.; see this paper : Article Anion-Regulated Hydroxysulfide Monoliths as OER/ORR/HER Elec...
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