Study on the Morphology and Fuel Cell Characteristics of a Modified Chitosan Membrane for Fuel Cell Application

Abstract

Development and characterization of polymer electrolyte membrane (PEM) using low cost Chitosan were carried out by blending with sulphonated zirconium oxide, and assessed for its potential to serve as possible polymer electrolyte membrane fuel cell (PEMFC) application. Synthesized membranes were thus characterized by scan electron microscope (SEM) to define the morphology of the membrane. Fourier Transform Infra-red (FT-IR) to confirm the presence of functional groups. Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) were used to verify the thermal stability of the membrane. Membrane water uptake was used to investigate the porosity and swelling ability of the membrane, while impedance spectroscopy was used to measure the proton conductivity of the membrane. The permeability of the membrane was determined using a diffusion cell that was developed at Vaal University of Technology. The results obtained revealed that the blending of the chitosan with sulphonated zirconium oxide improved the water uptake, thermal stability, proton conductivity and permeability of the composite membrane than Nafion 117, which is the commercially available membrane. The water uptake was in the range of 70-74% while that of Nafion 117 is in the bracket of 25-33%. The TGA and DSC analysis showed that the composite membrane developed is a glassy polymer with a glass transition temperature (T g ) of 184 o C. The proton conductivities were in the range of 10 -3 -10 -2 S/cm and tend to increase with increase in the composition of the sulphonated zirconium oxide use in synthesizing the composite membrane. The permeability obtained was in the range of 4 x 10 -6 – 7 x 10 -6 mol/m 2 .s.Pa. From the results of the proton conductivity and the permeability, the selectivity factor of the membrane, which is a measure of performance of the membrane were determined. This is in the range of 14 – 34.