Ferric sulfophenyl phosphate bonded with phosphotungstic acid as a novel intercalated high-temperature inorganic-organic proton conductor

A novel proton conductor was synthesized by intercalation of phosphotungstic acid (PWA) into layered ferric sulfophenyl phosphate (FeSPP) via in-situ polymerization. Fe-O-W covalent bonds were formed between FeSPP and PWA in the synthesized intercalated proton conductor (FeSPP-PWA). FeSPP-PWA with a PWA content of up to 42 wt% remained the layered structure of FeSPP. FeSPP-PWA exhibited good thermal stability up to 200 degrees C. The ion-exchange capacity of FeSPP-PWA(15 wt%) was 1.73 meq g(-1). Its proton conductivity was 0.14, 6.6 x 10(-2) and 1.65 x 10(-2) S cm(-1) at 100%, 50% and 0 RH at 180 degrees C, respectively, corresponding to the activation energy of 15.2, 17.3 and 27.0 kJ mol(-1), respectively. After washing for 12 and 24h, the conductivity of FeSPP-PWA(15 wt%) at 180 degrees C at 100% RH reduced by 1.5% and 1.7%, respectively. In comparison, the proton conductor prepared by direct mixing of FeSPP and PWA showed lower proton conductivity and poorer washing fastness than FeSPP-PWA. Intercalation of PWA into FeSPP proved to be an effective method for the preparation of high performance proton conductor. (C) 2018 Elsevier B.V. All rights reserved.