Starch-chitosan-ionic liquids-based composite membranes for high temperature PEM fuel cells applications

This work reports the fabrication of a starch-chitosan-based membrane for proton exchange membrane fuel cell applications at high temperatures, up to 145 °C. The membranes were fabricated by the solution casting method. Ionic liquids (ILs) were incorporated into the fabricated membranes to examine how they impact the proton conductivity. All the modified membranes generally demonstrated very good proton conductivity values in the range of 10−3 S/cm at room temperature. A noticeable increase in the proton conductivity was observed as the temperature was increased for the IL-based membranes. The IL-based membranes gave very high proton conductivities at 145 °C with a percentage increase of 209 % and 900 % compared to the reference membrane that contains starch and chitosan without any additives. The study reported structural interactions, particularly with the hydrophilic groups like the hydroxyl group, as revealed by FTIR analysis. These findings were supported by EIS measurements. The SEM images showed morphological alterations, and the XRD characterization indicated a shift toward an amorphous structure, implying more water retention in the polymer matrix, which explains the improved proton conductivity. The proton conductivity results as well as relevant water uptake properties reported in this work, appear to be promising for fuel cells operating above the boiling point of water.