Polymer/ZIFs membranes for proton conductivity: a mathematical modeling study

The Zeolitic Imidazolate Frameworks (ZIFs), specifically ZIF-90, were synthesized and incorporated as fillers in the fabrication of composite membranes using sulfonated poly (1,4-phenylene ether-ether-sulfone) (SPEES). The inclusion of ZIF-90 in the polymeric matrix demonstrated an improved enhancement in proton transport compared to that observed for SPEES or standalone ZIFs. Subsequently, a mathematical model was developed to forecast proton conductivity under diverse temperature and water content conditions. The modeling exhibited remarkable concordance with the experimental findings. In the subsequent phase of this study, electrochemical impedance spectroscopy (EIS) was employed to assess the real and imaginary components of complex conductivity. The temperature and frequency dependence of the real part of the conductivity were scrutinized. Additionally, tan(delta) analysis was performed for membrane under scrutiny, and the resulting value was applied to ascertain the diffusion coefficient through the analysis of electrode polarization (EP). The findings indicated a diffusion coefficient of 2.41 x 10-5 cm2/s for the SPEES membrane, whereas for the SPEES/ZIF-90 membrane, the value stood at 2.01 x 10-4 cm2/s at 80 degrees C. These results suggest that ZIF-90 holds significant promise as a filler in composite membranes, contributing to the improvement of proton transport properties.