Fuel cells with H3PW12O40 center dot 29H(2)O as solid electrolyte

Electrochemical activity tests have been performed on a fuel cell fed with H-2/O-2 at room temperature utilizing phosphotungstic acid (PWA) as solid electrolyte. Two different procedures were followed to prepare the electrolyte layers. One consisted of mixing the precursor of a silicon polymer with the crystalline powder of the PWA in an agate mortar and spreading the paste on a glass surface or on the surface of an electrode; the polymerization occurred with the layer already formed. A composite elastic material which held the acid entrapped in the pores of the polymer was obtained, The other procedure consisted of impregnating an inert porous material with a concentrate solution of PWA, for a longer time, to obtain a flat layer after successive drying. A stiff and undeformable material reinforced by the porous matrix was obtained by this method. Poor fuel cell electrochemical performances were obtained with the composite electrolyte layer principally due to the high protonic internal resistance. Moreover, the polymeric skeleton was unstable under the working conditions of the cell. Maximum power density of 0.075 W/cm(2) was obtained at 0.2 A/cm(2) with the electrolyte layer formed by 70 wt% of PWA and 30 wt% of silicone polymer. Better electrochemical fuel cell performance was obtained with the reinforced electrolyte layer containing glass microfibers prepared by the second method. This can be summarized in current density of 0.45 and 2.0 A/cm(2) at cell potential of 0.6 and 0.33 V, respectively, power density of 0.738 W/cm(2) at 1.8 A/cm(2) and a Tafel slope of 0.058 V/decade. (C) 1997 International Association for Hydrogen Energy.