Preparation and investigations of ABPBI membrane for HT-PEMFC by immersion precipitation method

Abstract

Poly(2,5-benzimidazole) (ABPBI) membranes were prepared by an easy and benign ‘immersion precipitation’ method; alleviating drawbacks of conventional solution casting method involving evaporation of the corrosive solvent. The importance of varying inherent viscosity on the properties of resulting membranes was investigated. The porous membranes formed by immersion precipitation method were analyzed for basic properties (water flux, porosity and dimensional analysis). Since the dense structure is required for their applicability for a fuel cell, through-porosity of the formed membranes was successfully eliminated using a unique shrinkage (~50%) property of ABPBI, initially, at 60 °C followed by at higher temperature. The correlation of membranes annealing temperature with the mechanical properties, phosphoric acid doping and proton conductivity was established. The present membranes exhibited high doping level (5.1 mol/RU), proton conductivity (0.083 S cm−1) and fuel cell performance. For comparison, solution casted membranes were prepared and analyzed. The OCP (0.91 V) and max power density (766 mW cm−2) are quite promising features of this new type of membranes.