Organic-inorganic composite membranes as addition of SiO2 for high temperature-operation in polymer electrolyte membrane fuel cells (PEMFCs)

Organic-inorganic composite membranes for operation above 100 deg. C in polymer electrolyte membrane fuel cells (PEMFCs) were prepared, characterized and cell-tested. Composite membranes were obtained by mixing organic polymers, which have a SO3H group as a proton conductor with inorganic material, SiO2, using the sol-gel process. Electron probe micro analyser (EPMA) was used to show the homogeneous and uniform distribution of SiO2. The physico-chemical properties of all membranes were investigated regarding their tensile strength, water uptake and thermogravimetric analyzer (TGA). Due to a higher water uptake and thermal stability of composite membranes, the cell performances at high temperatures above 100 deg. C, were improved. In addition, the SiOH group in the composite membrane was shown to play a major role in capturing water strongly and maintaining proton conductivity even at high temperature. Furthermore, the fuel cell performance of organic-inorganic composite membranes was superior to that of the Nafion membrane at high current density over all ranges of temperature