Polybenzimidazole membranes modified with polyelectrolyte-functionalized multiwalled carbon nanotubes for proton exchange membrane fuel cells

Abstract

Nafion-and polybenzimidazole (PBI)-functionalized multiwalled carbon nanotubes (MWCNT-Nafion and MWCNT-PBI) have been prepared through an ozone mediated process and used as additives in the preparation of PBI/MWCNT nanocomposite membranes. Scanning electron microscopy images of the nanocomposite membranes show a high compatibility between functionalized-MWCNTs and the PBI matrix. Addition of the functionalized MWCNTs enhances the thermal and mechanical properties of the composite membranes. Moreover, compared to the proton conductivity of 0.03 S cm(-1) of the phosphoric acid (PA)-doped PBI membrane, the PA-doped nanocomposite membranes containing 0.2 wt% of MWCNT-Nafion (N-0.2) and MWCNT-PBI (P-0.2) have proton conductivities of 0.05 and 0.08 S cm(-1) at 160 degrees C under anhydrous conditions, respectively. In single cell tests at 150 degrees C, N-0.2 and P-0.2 demonstrated maximum power densities of 700 and 600 mW cm(-2), respectively. The values are much higher than that found with pristine PBI membrane (530 mW cm(-2)).