Superprotonic KH(PO3H)–SiO2 composite electrolyte for intermediate temperature fuel cells

Novel thin film composite electrolyte membranes, prepared by dispersion of nano-sized SiO2 particles in the solid acid compound KH(PO3H), can be operated under both oxidizing and reducing conditions. Long-term stable proton conductivity is observed at ∼140 °C, i.e., slightly above the superprotonic phase transition temperature of KH(PO3H), under conditions of relatively low humidification (pH2O ≈ 0.02 atm).