Composite organic-inorganic proton exchange membranes for H-2-O-2 fuel cells were fabricated by ionotropic gelation process combining a biopolymer (chitosan) with a heteropolyacid (silicotungstic acid). According to scanning electron microscopy analysis, compact, homogeneous and free-standing thin layers were synthesized. X-ray diffraction proved the crystallinity of the fabricated membranes and showed the presence of Chitosan Form I polymorph soon after the reticulation step and of the Form II polymorph after the functionalization step. Fourier-transform infrared spectroscopy demonstrated that the Keggin structure of the heteropolyacid is maintained inside the membrane even after the fabrication process. These membranes worked properly as proton conductors in a low-temperature (25 degrees C) fuel cell apparatus using hydrogen as fuel recording a promising power density peak of 268 mW cm(-2) with a Pt loading of 0.5 mg cm(-2). Graphic abstract