Pentadecatungstotrivanadodiphosphoric heteropoly acid with Dawson structure: Synthesis, conductivity and conductive mechanism

Abstract

A general strategy in terms of degradating and ion-exchange synthesis was used to design pentadecatungstotrivanadodiphosphoric heteropoly acid H₉P₂W₁₅V₃O₆₂·28H₂O with Dawson structure and excellent conductivity. The product was characterized by ICP-MS, IR, UV, XRD, ³¹P NMR, TG-DTA and electrochemical impedance spectroscopy (EIS). The results indicate that H₉P₂W₁₅V₃O₆₂·28H₂O possesses the Dawson structure. EIS measurements show a high conductivity (3.64 × 10⁻² S cm⁻¹ at 26 °C and 75% relative humidity), with an activation energy of 31.34 kJ mol⁻¹ for proton conduction. Its mechanism for proton conduction is the Vehicle mechanism.