Synthesis and characterization of a new proton-conducting material based on imidazole and selenic acid

A first representative of a new group of proton conducting materials, imidazolium selenate dihydrate: (IMD)2SeO4·2H2O, was successfully synthesized. The structural and thermal properties, proton conductivity, and the dynamics of the salt obtained were studied by different analytical methods including X-ray diffraction (XRD), differential scanning calorimetry (DSC), impedance spectroscopy, Fourier transform infrared spectroscopy (FTIR), and magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The structural studies showed that the selenate anions and imidazolium cations bridged by crystalline water molecules formed a network of hydrogen bonds. This network is essential for proton conduction. The highest value of proton conductivity in (IMD)2SeO4·2H2O was found to be approximately 10− 1 S/m at 333 K. The 13C MAS NMR spectrum indicates that the imidazolium rings undergo fast reorientations and contribute to the effective proton conduction process.

► A representative of a new group of proton conducting materials was obtained.
► The newly synthesized salt is based on imidazole (IMD) units and SeO4 tetrahedra.
► SeO4 and IMD ions bridged by crystalline H2O formed a network of hydrogen bonds.
► High proton conductivity σdc of the order of ~ 10− 1 S/m was obtained at 333 K.
► Reorientations of SeO4 and imidazolium groups are essential for proton conduction.