Electrochemical properties and chemical stabilities of (NH4)2SO4/TiO2 composites at intermediate temperatures

A proton-conductive electrolyte of (NH4)2SO4/TiO2 composite was synthesized, and its proton conductivity and chemical stability at intermediate temperatures were investigated. In the composite, partial decomposition of (NH4)2SO4 occurred at around 250 °C, and the resulting materials showed high proton conductivity. The highest conductivity achieved was 15 and 35 mS cm− 1 under dry and wet atmospheres at 250 °C, respectively. The temperature dependences of the conductivity were almost reversible in any conditions investigated, and the composite was relatively stable. Under a hydrogen atmosphere, however, the reduction of (NH4)2SO4 phase occurred and the formation of H2S was observed.