Hybrid membranes as an electrolyte for high-temperature proton exchange membrane fuel cells (PEMFCs) were prepared from a Nafion polymer matrix with NH4 + /H3O+-β"-aluminas as an inorganic filler that has fast proton conductivity. The membranes, containing 5-20 wt% of filler, were obtained with a fairly uniform thickness of about 80 μm. The properties of the hybrid membranes - such as thermal stability, water uptake, proton conductivity, methanol crossover, and proton selectivity - were measured in the 25-120 oC temperature range and compared to those of Nafion®. The hybrid membranes became more thermally stable, showing a mere 2 wt% of water loss at 120 oC; they also had advantages over Nafion® in terms of water uptake, methanol crossover, and selectivity. The proton conductivities of the hybrid membranes generally lowered compared to Nafion®; however, they were maintained sufficiently for an electrolyte, representing 1.6 × 10−1 and 1.8 × 10−1 S/cm at 100 and 120 oC in the H3O+-β"-aluminas/Nafion® hybrid membrane, respectively

Keywords: Hybrid membrane, β"-alumina, High-temperature PEMFCs.