Synthesis and characterization of hydrated phosphor-silicate glass membrane prepared by an accelerated sol-gel process with water/vapor management

A series of inorganic proton conductive electrolytes based on hydrated phosphor-silicate glass [xP(2)O(5)-(100 - x)SiO2, x = 10, 20, 30, 40 and 50, molar ratio] synthesized by an accelerated sol - gel process with water/vapor management are investigated here. Silicate glass membranes with high P2O5 content can be synthesized successfully in a short time (similar to 3 days) by the developed process. Due to the formation of the P2O5 and SiO2 network structure, the hydrated phosphor silicate glass membranes show good thermal stability. Two or three kinds of pore sizes existing in the synthesized glass membranes were observed. Increasing the P2O5 content of the glass membrane leads to a decrease of its major pore size and an increase of its porosity. However, it was observed that the pore size of the glass membrane becomes larger when its P2O5 content is higher than 40%. The conductivity and the methanol permeability increase with increasing the content of the P2O5, and interestingly, a maximum selectivity (the ratio of the conductivity to permeability) occurs at the 30P(2)O(5)-70SiO(2) glass membrane. The glass membranes shows slightly lower conductivity but much higher selectivity compared with the Nafion 117 membrane. The effect of the P2O5 content on the properties of the glass membrane is also characterized and discussed.