Chemical oxidative degradation of Polybenzimidazole in simulated environment of fuel cells

The chemical oxidative degradation process of poly [2,2′-(m-phenylene)-5,5′-bibenzimidazole] (PBI) in simulated environment of fuel cells was evaluated. From the mechanical properties and the intrinsic viscosity of PBI, it was observed that the stress at break of PBI membranes decreased and the macromolecular chains of PBI were broken after the treatment in Fenton reagent for 24 h. From the photos of Scanning Electron Microscope, it was identified that there were lots of corroded holes in PBI membranes. By means of FTIR and 1H NMR analysis, it was shown that during the treatment of PBI in the presence of HO or HOO free radicals the hydrogen atom of N-H bond in imidazole ring was liable to be oxidized, and the phenyl was oxidized with the formation of quinine and dicarboxylic acid structures. In the end, the possible mechanism of the chemical oxidative degradation of PBI was proposed.