Self-humidifying novel chitosan-geopolymer hybrid membrane for fuel cell applications

Abstract

Novel, eco-friendly organic-inorganic hybrid, self-humidifying proton exchange membrane (PEM) series from chitosan (CS) were prepared by solvent-casting technique wherein heptanedioic acid (HA) is used as crosslinker and geopolymer (GP), an inorganic aluminosilicate material as the filler. FTIR, solid state NMR, SEM and XRD analysis revealed the formation of super-compatible CS-HA-GP hybrid membranes. Good self-humidification, appreciable proton conductivity, thermal stability and porosity were exhibited by the membranes. Thermokinetic behaviour of the membranes was studied using Broido's approximation method and the activation energy for different thermal degradation stages was deduced. The hybrid membrane with a concentration of 1.5 wt% of the crosslinker and 0.5 wt% of the filler showed excellent water retention, considerable porosity, highest proton conductivity of 4.12 × 10^-3 Scm^-1, appreciable thermal, mechanical as well as oxidative stability and high activation energy, is considered as the optimum composition. The above results suggest the suitability of these novel hybrid membranes as substitutes for Nafion in fuel cells.

Keywords: Chitosan; Geopolymer; Hybrid membranes; Proton conductivity; Proton exchange membrane fuel cells; Self-humidification.