Novel mild conversion routes of surface-modified nano zirconium oxide precursor to layered proton conductors

Abstract

Layered proton conductors of three different materials, zirconium phosphate (ZrP), zirconium sulfophenylphosphonate (ZrSPP), and zirconium sulfate (ZrS) were synthesized from the same surface-modified nano zirconium oxide precursor through novel, mild conversion routes. The conversions were performed at 80 °C under mild acidic conditions. The phase formation of ZrP, ZrSPP, and ZrS were confirmed by FT-IR and XRD techniques. Thermal stabilities of ZrSPP and ZrS were evaluated by thermogravimetric analysis and hydrothermal tests at 150 °C for 24 h. Proton conductivities of ZrP, ZrSPP, and ZrS were measured at 90 °C under various relative humidities. The mild conversion routes will enable in situ synthesis of these layered proton conductors inside a polymer matrix from the same nano zirconium oxide precursor, which has been reported to form a nanodispersed structure in polymer electrolytes such as perfluorosulfonated ionomers and aromatic hydrocarbon electrolytes.