Recent advances in the functionalisation of polybenzimidazole and polyetherketone for fuel cell applications

This article reviews progress made over the past years in the functionalisation of polybenzimidazole and polyetherketones with a view to increasing their proton conduction properties without detriment to their thermohydrolytic and chemical stability such that corresponding membranes may be employed in hydrogen oxygen (air) or direct methanol fuel cells. The approaches include complexation of polybenzimidazole with acids, grafting of groups containing sulfonic acid moieties on to polybenzimidazole by N-substitution, and direct sulfonation of polyetherketones. A further approach concerns the incorporation of inorganic proton conducting particles in the polymer matrix, and this is developed in detail for the case of hybrid sulfonated polyetheretherketone–metal(IV) phosphate membranes.