Polybenzimidazole-Clay Nanocomposite Membrane for PEM fuel cell: Effect of organomodifier structure

Abstract

In this work, montmorillonite clay was organically modified using two surfactants which are largely different in their chemical structure - one is dimethyldihydrogenated ammonium chloride tallow (DDACT), that contains two long alkyl chains and the other is tributyl phosphonium molecule (TPB), a molecule containing short alkyl chains. The objective of the work is to study the effect of these surfactants’ structure on the properties of OPBI for proton exchange membrane (PEM) fuel cell applications. The morphology study of the membranes using PXRD and TEM revealed intercalated nanostructures using both the clays. The increment in thermal stability and T g was found to be higher in the case of TPB modified clay membranes than the tallow amine modified clay membranes. Acid doping and swelling studies were performed and the values again reflected the nature of the surfactant used with phosphonium cation containing membranes showing higher PA doping levels. Specific swelling volume of the membranes portrayed the controlled swelling behaviour of all the nanocomposite membranes. Proton conductivity of the membranes were found to be lower than the pristine OPBI owing to the tortuous conduction pathway created by the clay sheets.