SYNTHESIS AND CHARACTERIZATION OF MWCNT-SUPPORTED PBI MEMBRANES FOR HT-PEM FUEL CELLS

Polybenzimidazole (PBI) membranes are highly sought after for HT-PEMFCs due to their thermal stability, mechanical strength and protonic conductivity. In this study, PBI polymer and the membranes were synthesized for HT-PEMFC applications. Then, the polymer was characterized by using NMR and TG analyses. All the characteristic peaks were observed in the NMR results and PBI polymer decompose around 550 °C. After the synthesis, pristine and multi-walled carbon nanotube (MWCNT) supported membranes were prepared, doped with phosphoric acid and characterized by using TGA, FT-IR, XRD, SEM and EIS tests. The characteristic bonds of the polymer for both undoped and doped membranes were seen in FT-IR results. XRD results showed the semi-crystalline structure of the polymer. SEM results enabled to observe the homogeneous dispersion of the MWCNTs within the membrane. Finally, EIS tests were carried out in anhydrous conditions. The conductivities were obtained for pristine PBI membrane as 0.0518 S/cm, 0.0667 S/cm and 0.0895 S/cm, respectively. For the 0.5wt% PBI/MWCNT membrane, they were calculated as 0.0401 S/cm, 0.0586 S/cm and 0.0613 S/cm for 120 °C, 140 °C and 160 °C, respectively. For the 1wt% PBI/MWCNT membrane, slightly higher conductivities were obtained as 0.0429 S/cm, 0.0621 S/cm and 0.0655 S/cm for the temperatures 120 °C, 140 °C and 160 °C, respectively.