Properties of PWA/ZrO2-doped phosphosilicate glass composite membranes for low-temperature H2/O2 fuel cell applications

Phosphosilicate doped with a mixture of phosphotungstic acid and zirconium oxide (PWA/ZrO2-P2O2-SiO2) was investigated as potential glass composite membranes for use as H-2/O-2 fuel cell electrolytes. The glass membranes were studied with respect to their structural and thermal properties, proton conductivity, pore characteristics, hydrogen permeability, and performance in fuel cell tests. Thermal analysis including TG and DTA confirmed that the glass was thermally stable up to 400 degrees C. The dependence of the conductivity on the humidity was discussed based on the PWA content in the glass composite membranes. The proton transfer in the nanopores of the PWA/ZrO2-P2O5-SiO2 glasses was investigated and it was found that a glass with a pore size of similar to 3 nm diameters was more appropriate for fast proton conduction. The hydrogen permeability rate was calculated at various temperatures, and was found to be comparatively higher than for membranes based on Nafion(R). The performance of a membrane electrolyte assembly (MEA) was influenced by its PWA content; a power density of 43 mW/cm(2) was obtained at 27 degrees C and 30% relative humidity for a PWA/ZrO2-P2O5-SiO2 glass membrane with a composition of 6-2-5-87 mol% and 0.2 mg/cm(2) of Pt/C loaded on the electrode. (C) 2008 Published by Elsevier B.V.