Synthesis and characterization of NH4PO3 based composite with superior proton conductivity for intermediate temperature fuel cells

In this work, we prepared NH4PO3/MO2 (MSi, Ti) composite materials with various amounts of TiO2 using a sol–gel method, which are potential for application as electrolytes for intermediate temperature fuel cells (150–250 °C). The effect of the amount of TiO2 on the conductivities of the composite was investigated systematically by an impedance spectroscopy within the temperature range of 50–275 °C under different atmospheres. The composite SiTiO10APP (10 mol% TiO2) showed high proton conductivity, 0.001–0.043 S cm−1 at 150–250 °C. The maximum conductivities are 0.043 S cm−1 at 225 °C under humid H2 and 0.0085 S cm−1 at 175 °C under humid air, respectively. A thermogravimetric analysis showed the composite had high thermal stability below 300 °C. Moreover, it was found that the microstructure has significant effect on the conductivity of the composites at higher temperature.