Solid state NMR investigation of hydrous ruthenium oxide

Amorphous hydrous ruthenium oxide (RuO₂·xH₂O) with different composition x has been studied using solid-state nuclear magnetic resonance (NMR) spectroscopy. The ²DNMR spectra at different temperatures illustrate that the water molecules undergo fast molecular motion even if the temperature is as low as 213 K. The static ¹HNMR spectra indicate the composition dependent proton-proton dipolar interaction. It is demonstrated that the mobility of the water molecules and their interaction with ruthenium oxides play an important role in the proton charge density. In conclusion, the competition between these two antithetical effects provides a mechanism for the proton charge storage of the RuO₂·xH₂O materials.