Hydrogen Motion of CsH2PO4 Electrolyte Using 1H and 31P High-Resolution Nuclear Magnetic Resonance (NMR) Spectroscopy

This study investigated hydrogen-bonded CsH2PO4 (CDP) solid acid using 1H and 31P high-resolution nuclear magnetic resonance (NMR). Below the superprotonic phase transition temperature, the temperature dependence of the 1H NMR spectra was observed with two different hydrogen-bonded networks in the CDP structure. The systematic evolution of the lineshape with temperature dependence indicates hydrogen hopping in the chemical structure of hydrogen-bonded networks in a solid acid lattice. The proton conduction under two types of hydrogen-bonds—interchain and intrachain—in CsH2PO4 in the chemical environments of PO4 tetrahedra is discussed.

THERMAL AND ELECTRICAL BEHAVIOUR OF THE SUPERPROTONIC CONDUCTOR PHASE IN Rb2(HSeO4)1.5(H2AsO4)0.5

Crystals of a new compound with a superprotonic phase transition Rb2(HSeO4)1.5(H2AsO4)0.5 (noted RbHSeAs), were synthesized by slow evaporation of an aqueous solution at room temperature. The differential scanning calorimetric analyses showed two endothermic peaks at 465 K and 566 K. The last peak corresponds to the decomposition of the material. The first transition was characterized by several techniques (impedance spectroscopy, complex modulus, Raman and X-ray diffraction powder depending on temperature). ac impedance measurements revealed that, upon heating, the compound undergoes at ~ 443 K a sharp increase in conductivity from a low temperature protonic phase to a superprotonic conductivity phase. The activation energies calculated from the modulus (Ef) and impedance (E) spectra respectively are approximately equal, suggesting that the transport properties in this material above and below the superprotonic phase transition (443 K) are probably due to an H+ protons hopping mechanism.