it is not necessary that it will intercept with the real axis

as Ranjan K. Mallick. Also, it (EIS graph) seems essentially close to a case study in (your model) ref[1].

1.  Figure 6. Impedance spectra .... at low light intensity,...  (https://goo.gl/wTM4YT)

Dear Raihan Choudhury,

to see the intercept with real axis (and to define the internal resistance of your MCFC cell) you can change the starting frequency. I mean that you have to increase the starting value at high frequency. At the same time you can try to decrease the final point at low frequency to check the arc in the cathode side.

Regards

G.A.

I am curious about your system. Have you put excess amount of electrolyte in your cell?Have you used any reference electrodes when you measure EIS? and which type of reference electrodes have you used? If you don't use reference electrode to study, I don't think you could easily separate cathode and anode polarization, especially at 700oC, the electrolyte (62:38) has trend to evaporate much faster than at lower temperature.

Thanks to Mr. Ranjan K. Mallick, Mr. Ioannis Samaras  and Madam Grazia Accardo  for kind support.

Dear Mr. Hoang Viet Phuc Nguyen,

Here are my answer for your questions:-

Q1. Have you put excess amount of electrolyte in your cell?

A: Yes. Almost 100 times more.

Q2.Have you used any reference electrodes when you measure EIS?and which type of reference electrodes have you used?

A: Nope. This EIS graph is for full cell. Moreover we used a novel design. So it is difficult to put Ref there.

Please let me know what do you think?