Preparation of hydrous ruthenium oxide/carbon black nanocomposite material was performed by the impregnation method starting from hydrous RuO2 sol as a precursor. Black Pearls 2000 (R) (BP) and Vulcan (R) XC-72 R (XC) was used as supporting materials. Chemical and structural characterization of the precursor and the composites was performed by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), energy-dispersive X-ray fluorescence spectroscopy (EDXRFS), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). These techniques showed hydrous and amorphous structure of the oxide impregnated into the carbon support. The capacitive properties of both carbon supporting materials and composites will be discussed in forthcoming parts of this paper