Synthesis and high proton conductivity of an indium-substituted Keggin-type quaternary heteropoly acid

Abstract

The synthesis and characterization of an indium-substituted quaternary heteropoly acid with a Keggin structure, H₄[In(H₂O)PW₉Mo₂O₃₉]·11H₂O (PMo₉W₂In), is reported. At 18 °C under 80% relative humidity, PMo₉W₂In displays protonic conductivity of 2.32 × 10⁻⁴ S cm⁻¹ with an activation energy of 35.52 kJ mol⁻¹, indicating that it is a potential solid protonic conductor following the vehicle mechanism. Its conductivity increases with temperature in the measured temperature range.