A carbon-based electrostatic double-layer supercapacitor using a proton conducting electrolyte (Nylon 6-10, 2H(3)PO(4)) has been developed and its performances are compared to those of the same device using an aqueous electrolyte (H3PO4, 7.3 M). Impedance spectroscopy has also been applied to the characterization of the supercapacitors in the -5 to 55 degrees C temperature range.