Search

Cesium dihydrogen phosphate (CsH2PO4, CDP) and dodecaphosphotungstic acid (H3PW12O40·nH2O, WPA·nH2O) were mechanochemically milled to synthesize CDP-WPA composites. The ionic conductivities of these composites were measured by an ac impedance method under anhydrous conditions. Despite the synthesis temperatures being much lower than the dehydration and phase-transition temperatures of CDP under anhydrous conditions, the ionic conductivities of the studied composites increased significantly. The highest ionic conductivity of 6.58×10-4 Scm-1 was achieved for the 95CDP·5WPA composite electrolyte at 170 °C under anhydrous conditions. The ionic conduction was probably induced in the percolated interfacial phase between CDP and WPA. The phenomenon of high ionic conduction differs for the CDP-WPA composite and pure CDP or pure WPA under anhydrous conditions. The newly developed hydrogen interaction between CDP and WPA supports anhydrous proton conduction in the composites. [ABSTRACT FROM AUTHOR]

Abstract: A typical solid acid of CsHSO4 and phosphotungstic acid (H3PW12O406H2O: WPA6H2O) were mechanically milled, and non-humidified proton conductivity of the obtained composite was investigated. The 90CsHSO410WPA (mol%) composite showed high proton conductivities of 10−2–10−4 S/cm from 160 to 30 °C under dry nitrogen atmosphere, while the conductivity of pure CsHSO4 dropped abruptly at around 145 °C due to the phase transition from superprotonic CsHSO4(I) phase to CsHSO4(II) phase. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy measurements were performed at various temperatures to study the phase transition behaviour as well as hydrogen bonding structure. The phase transition was not observed for the 90CsHSO410WPA composite. FTIR measurements revealed that a peak for OH stretching shifted to a higher wavenumber with increasing temperature. The O–H•••O hydrogen bond distance was calculated from the OH band wavenumber. The proton conductivities in dry conditions were related to the bonding distance. [Copyright &y& Elsevier]

Abstract: CsHSO4 and dodecatungstophosphoric acid (H3PW12O40·6H2O:WPA·6H2O) were mechanically milled to synthesize xCsHSO4·(100− x)WPA (mol%) composites. 1H NMR measurements suggested that a hydrogen bond was newly developed between WPA and CsHSO4, and proton transfer at CsHSO4–WPA composite region was considered to be faster than that at pure CsHSO4 or WPA. Proton conductivity of the 90CsHSO4·10WPA (mol%) composite at 100 °C showed much higher of 3.3×10−3 S/cm than that of pure CsHSO4 (4×10−7 S/cm) or that of WPA(1×10−7 S/cm). The –O(H)···O hydrogen bonding distance was estimated from the 1H-isotropic chemical shift of 1H MAS NMR spectra. The proton conductivities in dry atmosphere of CsHSO4·WPA composites were strongly correlated with the O(H)···O bond distance L. [Copyright &y& Elsevier]