Home – Home – Jornals – Chemistry for Sustainable Development 2021 number 5

The structural, morphological and electrochemical properties of nanocomposite materials of the type of a highly porous carbon matrix filled with Co₃O₄ are investigated. The effect of the filler preparation method (thermal decomposition of cobalt (II) hydroxide or cobalt (II) azide) in matrix pores on the characteristics of composites was considered. The composition, morphology, phase compositions of the composites, the stoichiometry of fillers, disperse and porous structures, as well as electric capacitance characteristics of the carbon matrix, precursor composites and nanostructured C/Co₃O₄ composites were studied using various physicochemical methods. It is established that the composites are formed through the deposition of nanoparticles of filler precursor and, during their thermal decomposition, of the target filler Co₃O₄ in the pores of three size groups (2-3, 7-12, and ~20 nm), and through the formation of the aggregates of filler particles on the external surface of the matrix. The nature of the effect of filler on the electric capacity of the composite depends on the method of composite formation: the capacity decreases in the composites obtained by thermal decomposition of Co(OH)₂ precursor and, quite contrary, increases in the composites formed by thermal decomposition of Co(N₃)₂. This feature, discovered for the first time, may be related to the effect of the method of composite preparation on filler stoichiometry (the Co²⁺/Co³⁺ ratio) as determined by X-ray diffraction: the deviation of the stoichiometry from the formula-based relations between CoO and Co₂O₃ proceeds towards an increase in CoO fraction when the azide precursor is used, and towards an increase in the fraction of Co₂O₃ when the hydroxide precursor is used.