Preparation and Electrochemical Performance of Tungstovanadophosphoric Heteropoly Acid and Its Hybrid Materials

Tungstovanadophosphoric heteropoly acid H6PW9V3O40 center dot(13.81 +/- 0.13)H2O (abbreviated as PW9V3) has been synthesized by the stepwise acidification and the stepwise addition of element solutions. The crystal structure was determined from single crystal X-ray diffraction. The complex crystallizes in the space group R (3) over barm, with a = 16.4374 (9) angstrom, b = 16.4374 (9) angstrom, c = 25.3866 (14) angstrom, alpha = 90, beta = 90 degrees, gamma = 120, V = 5940.20 angstrom, and Z = 6. The product possesses Keggin structure, and its conductivity was 1.730 x 10(-2) S.cm(-1) at 26 degrees C and 75% relative humidity by electrochemical impedance spectroscopy (EIS) measurement. Two conducting systems were prepared with a mixture of as-synthesized PW9V3 and organic polymers [polyvinylpyrrolidone (PVP) or polyethylene glycol (PEG)] at the weight ratio 80:20. The hybrid materials exhibit high proton conductivities with 7.110 x 10(-3) and 1.050 x 10(-2) S.cm(-1) (PW9V3/PEG) at 26 degrees C and 75% relative humidity, respectively. Their activation energies of proton conduction are 15.23 and 13.67 kJ.mol(-1), which are lower than that of pristine heteropoly acid (25.68 kJ.mol(-1)). Their mechanisms of proton conduction are also proposed.