Three-dimensional hydrogen-bonding networks and proton conductivities under non-humidified conditions of CsHSO4–WPA composites

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.