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 H<inf>3</inf>PW<inf>12</inf>O<inf>40</inf>. 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 NH<inf>2</inf> groups and PTA^3- ions with preserved Keggin structure. Membranes were tested as proton conductor in low temperature H<inf>2</inf>-O<inf>2</inf> fuel cell allowing to get peak power densities up to 300mWcm^-2. Electrochemical impedance measurements allowed to estimate polyelectrolytes' conductivity up to 28mScm^-1 at room temperature.