On the development of proton conducting P2O5–ZrO2–SiO2 glasses for fuel cell electrolytes

Proton conductivity was examined in P2O5–ZrO2–SiO2 glasses prepared by sol–gel method and characterized for structural, nitrogen adsorption–desorption and thermal measurements. The amorphous phases of our glasses were confirmed by X-ray diffraction (XRD) analysis. Fourier transform infrared (FTIR) spectroscopy studies identified the presence of SiOSi and ZrOSi bond structures on glass surface. The differential thermal analysis and thermal gravimetric analysis (TGA/DTA) results showed decomposition in the temperature range from 40 to 300 °C. A distribution of average pore size 2.5 nm, pore volume 0.26 cm3 g−1 and surface area 407 m2 g−1 were obtained by pore analysis. Proton conductivities of all samples (thickness 0.5–1 mm) increased with an increase in relative humidity (RH) (40–90%), indicating that continuous paths suitable for proton conduction were formed in the glasses heat treated at 600 °C due to the adsorption of water. The temperature dependence of the conductivity for all compositions increases with increasing temperature range of 30–90 °C at relative humidity 70%. An open circuit potential of ∼1 V and a maximum power density of about 0.9 mW cm−2 were achieved at 30 °C with relative humidity 30%.