Well, I'm not an expert (actually, I'm a beginner in this field and I'm still learning) but I think that *at first* you have to know (or at least, you have to reasonably guess) what is happening in your electrochemical cell, i.e. what are the physical processed involved in it, and then you can build a suitable model circuit and try to fit your data. It looks like you're doing it the other way around. Don't know, maybe I misunderstood your question.

Thank you very much. I think I would try to understand the model circuit first. Being a physicist, I do not have substantial Chemistry background and so am finding it a bit difficult to relate to these electrochemical processes. I have been referring to Bard and Faulkner but still I haven't understood much.

Dear Suraj

You can post your data if you wish so people can give you more precise pointers.

Dear Dave,

I appreciate your advice. I am uploading an image of the Nyquist plot that I have recorded for one of my samples. Hope this will give others an idea of my situation.

It looks like you might have 2 time constants although the first one looks odd. Do you want to upload your data as well (in ASCII text format)?

Hi Christian,

Thanks for your consideration. I have been studying electrocatalysts for alkaline water splitting. The electrode used is a powder material which is pressed at high pressures and the effective surface area projected is 1cm2. For EIS spectra, the range chosen is 100 Hz - 1MHz and amplitude is 50 mV.

Please tell me how to plot the curves on equal axes?? And what should be the ideal potential to take EIS spectra - OCP or equilibrium??