Structural and Transport Properties of Mixed Phosphotungstic Acid/Phosphomolybdic Acid/SiO₂Glass Membranes for H₂/O₂Fuel Cells

The synthesis and characterization of a novel inorganic glass composite membrane consisting of a mixture of phosphotungstic acid and phosphomolybdic acid are reported. Phosphosilicate gels doped with these two proton conducting donor components were derived by a sol−gel method. The influence of the textural properties of the glass composites could be interpreted from N 2 adsoption−desorption isotherms. The pore size was less than 6 nm for all glass membranes. These glass membranes were found to be stable up to 400 °C. Fourier transform infrared spectroscopy indicated that the characteristic Keggin anions PW 12 O 40 3- and PMo 12 O 40 3- were present in the glass composite membrane. The highest proton conductivity was measured to 1.01 × 10 - 1 S cm -1 at 85 °C with 85% relative humidity (RH). Membrane electrode assemblies were prepared and showed good performance, with a maximum power density value of 35 mW/cm 2 at 93 mA/cm 2 as well as a current density of 137 mA/cm 2 when utilized in a H 2 /O 2 fuel cell at 28 °C and 30% RH.