Enhanced conductivity in polyanion-containing polybenzimidazoles. Improved materials for proton-exchange membranes and PEM fuel cells

In an effort to develop improved Proton Exchange Membranes for Polymeric Fuel cells two different forms of polyanion inclusion in poly(2,5-benzimidazole) (ABPBI) have been carried out. Namely by (i) sulfonation of pre-formed polymer membranes and (ii) by addition of inorganic phosphomolybdic acid to form hybrid ABPBI-PMo₁₂ membranes. In both cases we have detected an increased proton conductivity of the resulting membranes, associated to an enhanced capacity of the polyanion-modified materials to uptake phosphoric acid (in comparison with previously known ABPBI or even commercial PBI membranes). These new membranes are stable up to 200 °C and feature high conductivities at these temperatures, which makes them promising candidates for higher-temperature PEM Fuel Cells.