Abstract <p>The formation of nanostructured composites by the thermal decomposition of transition metal nitrates in pores of a carbon matrix obtained in the carbonization of sapropelic coal is investigated. The nitrates—Co(NO₃)₂, Ni(NO₃)₂, Mn(NO₃)₂, Cu(NO₃)₂, Fe(NO₃)₃, Cr(NO₃)₃, and AgNO₃—are introduced in the matrix by adsorption from 0.5 M aqueous solutions. Emission spectroscopy with inductively bound plasma shows that the concentration of the transition metals in the nanostructured composites is 2–6 wt %. It is established by X-ray spectral analysis that the thermal decomposition products of the transition metal nitrates in the pores of the matrix are X-ray amorphous, except for AgNO₃ and Cu(NO₃)₂, probably because the particles formed are small. Adsorption porosimetry indicates that the specific surface and pore volume of the carbon matrix are slightly reduced when introducing the filler by this means. According to derivatographic data, carbon matrices containing the precursor of the filler are less resistant to thermal oxidation in air, probably on account of catalysis by the transition metal oxide nanoparticles that form. The electrochemical properties of the resulting nanostructured composites for electrode production are investigated by cyclic voltammetry. The results show that, in some cases, the introduction of filler by the thermal decomposition of transition metal nitrates yields composites whose unit electrical capacitance exceeds that of the initial matrix. The growth in unit electrical capacitance is greatest (20–25%) for nanostructured composites filled with the decomposition products of magnesium (II) and copper (II) nitrates.</p>