Electrochemical Impedance Spectroscopy (EIS) provides a versatile frequency-domain approach for probing transport and polarisation phenomena in porous crystalline materials. In this contribution, an in-situ impedance framework is applied to binder-free ZSM5 pellets exposed to controlled Ne and CO2 environments. The methodology combines Nyquist, Bode, loss-tangent (tanδ), and Distribution of Relaxation Times (DRT) analysis to qualitatively distinguish processes associated with transport at the pellet, intercrystalline and intracrystalline length scales.
Measurements are performed directly under the respective gas atmospheres, allowing the impedance response to reflect ongoing adsorption‑related changes. Exposure to gases generally leads to measurable modifications in the characteristic relaxation behaviour of the pellet, consistent with adjustments in the effective pathways available for transport. While both Ne and CO2 modify the pellet-scale impedance behaviour, CO2 typically shows a more visible effect in the higher-frequency part of the spectrum, which reflects its stronger interaction with the internal zeolite environment.
By combining characteristic time constants with diffusion-length considerations, the approach provides a qualitative framework for assessing multi-scale transport behaviour without relying on absolute diffusion values. The results show the potential of in-situ EIS as a complementary diagnostic tool for studying how different gas environments affect transport pathways in porous crystalline materials.

Literature:
Grün, R., Hashim, A.S., Grau Turuelo, C., Breitkopf, C., 2024. Insights into CO2 Diffusion on Zeolite 13X via Frequency Response Technique. Chemistry–Methods 4, e202400006. https://doi.org/10.1002/cmtd.202400006
Magar, H.S., Hassan, R.Y.A., Mulchandani, A., 2021. Electrochemical Impedance Spectroscopy (EIS): Principles, Construction, and Biosensing Applications. Sensors 21, 6578. https://doi.org/10.3390/s21196578