A CsH2PO4-based composite electrolyte membrane for intermediate temperature fuel cells

Solid acids are considered as a promising electrolyte for intermediate temperature fuel cells (ITFCs), but their application is hindered by their inherent shortcomings, including poor mechanical properties , limited chemical stability, low proton conductivity at low temperature and narrow high-conductivity temperature range. Despite much work devoted to addressing these shortcomings, none of them can tackle these issues simultaneously. In view of this, we reported a composite electrolyte membrane based on CsH 2 PO 4 , sulfonated poly(ether ether ketone) and phosphosilicate sol. The electrolyte membrane was fabricated by using a simple sol–gel process combined with mechanical ball-milling. The prepared electrolyte membrane exhibits excellent mechanical performance with a tensile strength of 23.5   MPa, despite an inorganics content of 70   wt%. The electrolyte membrane can keep intact even if it is heated to 260   °C. The measurement of proton conductivity shows that the electrolyte membrane can maintain a high conductivity of above 10 −3   S   cm −1 over a broad temperature range of 130–230   °C under ambient condition without humidifying. The successful fabrication of the electrolyte membrane not only provides a promising membrane for ITFCs, but also opens fresh insights for the development of electrolytes with superior comprehensive performance and the application of solid acids in ITFCs.