Preparation of proton conductive composites with cesium hydrogen sulfate and phosphosilicate gel

We prepared a new composite material composed of cesium hydrosulfate (CsHSO4) and phosphosilicate gel (P2O5–SiO2 gel); a high temperature form of the former exhibits exceptionally high proton conductivity at above 144 °C without humidification and the latter is one of the high proton conductors working under low humidity in a temperature range up to around 150 °C. High electric conductivities of 10− 5 to 10− 2 Scm− 1 of the composite were observed under dry N2 atmosphere in a wide temperature range from ambient to 160 °C and no steep change in conductivity at around 144 °C was observed. In X-ray diffraction pattern of CsHSO4–(P2O5–SiO2 gel) composites, new diffraction peaks were observed and original peaks of CsHSO4 disappeared. A reaction of CsHSO4 and orthophosphoric acid (H3PO4), which is probably formed by the hydrolysis of P2O5–SiO2 gel, would occur to produce a new crystalline phase with high proton conductivity at lower temperatures.