Synthesis and high proton conductive performance of a quaternary vanadomolybdotungstosilicic heteropoly acid

Abstract

A new vanadium and molybdenum-substituted quaternary silicon-containing heteropoly acid H6SiW9MoV2O40·15H2O has been synthesized in this paper by the stepwise acidification and the stepwise addition of elemental solutions. The structural feature and hydration of this product were characterized by IR, UV, XRD and TG-DTA, and its proton conductivity was measured by electrochemical impedance spectroscopy (EIS). The result of EIS shows that H6SiW9MoV2O40·15H2O is a solid high-proton conductor with a conductivity of 6.01 × 10(-3) S cm(-1) at 22 °C and 80% relative humidity, which increases at higher temperatures. Its conductive activation energy is 27.5 kJ mol(-1), which suggests that the mechanism of proton conduction is dominated by the vehicle mechanism.

Quaternary Vanado‐Molybdotungstophosphoric Acid [H5PW6Mo4V2O40] Over Natural Montmorillonite as a Heterogeneous Catalyst for the Synthesis 4H‐Pyran and Polyhydroquinoline Derivatives

“…The XRD diffraction patterns of newly prepared VMWP catalyst, nMont clay and 20 % nMont/VMWP are shown in (Figure ). The XRD pattern of VMWP catalyst showed major diffraction peaks in four ranges of 2 θ , which are 7–10°, 16–22°, 26–30° and 31–38° indicating typical features of the Keggin structure and crystalline state (Figure a) . On the other hand, naturally occurring montmorillonite clay (Figure b) shows three intense peaks at 2θ=7.09°, 19.93°, and 26.54° .…”

“…5 % appears endothermic peak at 158 °C for 3.6 protonized water molecules and the third exothermic peak appeared at 479 °C due to mass loss of 1.71 % of structural water molecules. The exothermic peak appeared at 479 °C were ascribed to the decomposition of the Keggin unit of VMWP to individual oxides, it indicating that this heteropoly acid will remain stable up to 479 °C . Due to lower thermal stability, VMWP supported on nMont clay.…”

“…The XRD pattern of VMWP catalyst showed major diffraction peaks in four ranges of 2θ, which are 7-10°, 16-22°, 26-30°a nd 31-38°indicating typical features of the Keggin structure and crystalline state (Figure 2a). [54] On the other hand, naturally occurring montmorillonite clay ( Figure 2b) shows three intense peaks at 2θ = 7.09°, 19.93°, and 26.54°. [5,55] Several other peaks were also observed which indicates that naturally occurring montmorillonite clay (nMont) was nano-crystalline in nature.…”

“…The exothermic peak appeared at 479°C were ascribed to the decomposition of the Keggin unit of VMWP to individual oxides, it indicating that this heteropoly acid will remain stable up to 479°C. [54] Due to lower thermal stability, VMWP supported on nMont clay. The TGA of 20 % nMont/VMWP showed about 9.8 % mass loss up to temperature at 295°C, which was attributed to the loss of adsorbed water molecules shown in Figure 7b.…”

A Novel Keggin-type Monovanadium-substituted Polyoxometalate-based Electrolyte

“…They are well-known electrochemically active materials with high conductivity and thermal stability, which makes them attractive as materials for energy sources with high power [4][5][6]. However, these HPAs suffer from diffusion problems and continuous leakage during cell operation, as well as most of them is crystalline powders, which hinder their practical utilization in electrochemical capacitor [7].…”