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

Abstract

A series of inorganic proton conductive electrolytes based on hydrated phosphor–silicate glass [xP₂O₅–(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 (∼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 30P₂O₅–70SiO₂ 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.