what is the material? show your spectra to make other understand? There is no definite way. if you all information then probably you can design your equivalent circuit. do not forget to mention frequency range as well.
i think R1 in series with parallel combination of R2 and CPE will do job. if your electrodes are porous then you should add CPE in parallel R1 too. try to fit this. i hope you will find good fit.