Synthesis and conductivity of heptadecatungstovanadodiphosphoric heteropoly acid with Dawson structure

Abstract

A new solid high-proton conductor, heptadecatungstovanadodiphosphoric heteropoly acid H7P2W17VO62· 28H2O with Dawson structure was synthesized by the stepwise acidification and the stepwise addition of element solutions. The optimal proportion of component compounds in the synthesis reaction was given. The product was characterized by chemical analysis, potentiometric titration, IR, UV, XRD, 31P NMR, TG-DTA and electrochemical impedance spectroscopy (EIS). The results indicate that H7P2W17VO 62·28H2O possesses the Dawson structure. EIS measurements show a high conductivity (3.10 × 10-2 S cm -1 at 26 °C and 75% relative humidity), with an activation energy of 32.23 kJ mol-1 for proton conduction. The mechanism of proton conduction for this heteropoly acid is Vehicle mechanism. © 2011 Elsevier B.V. All Rights Reserved.