Influence of synthesis conditions on the performance of chitosan-Heteropolyacid complexes as membranes for low temperature H2-O2 fuel cell

Flat, free-standing chitosan/phosphotungstic acid (PTA) polyelectrolyte membranes were prepared by in-situ ionotropic gelation process at room temperature on porous alumina support firstly impregnated by H3PW12O40. Scanning electron microscopy revealed the formation of compact and homogeneous membranes, whose thickness resulted to be dependent on chitosan concentration and reticulation time. X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) evidenced the formation of almost amorphous membrane without appreciable concentration of not protonated NH2 groups and PTA3− ions with preserved Keggin structure. Membranes were tested as proton conductor in low temperature H2-O2 fuel cell allowing to get peak power densities up to 300 mW cm−2. Electrochemical impedance measurements allowed to estimate polyelectrolytes' conductivity up to 28 mS cm−1 at room temperature.