Home – Home – Jornals – Chemistry for Sustainable Development 2019 number 6

Nanostructured composites Mn_xO_y/multiwalled carbon nanotubes (MCNT) with a mass ratio of Mn/MCNT 2 : 98; 5 : 95; 10 : 90 were prepared by the reduction of KMnO₄ aqueous solution on the surface of a carbon material (matrix) at a temperature of 25, 60 and 80 °C. Non-ozonized MCNT-1 and ozonized MCNT-2 were used as the carbon matrix. Nanocomposites were studied by means of X-ray phase analysis, small-angle scattering of X-ray radiation, and a complex of electrochemical methods. The influence of the conditions for producing nanocomposites (temperature, ultrasonic radiation) and the filler content on their electrical capacity characteristics were considered. It was determined that the optimal Mn/MCNT ratio was 5 : 95; with an increase in the content of manganese oxides (Mn/MCNT up to 10 : 90) and potential scanning rate higher than 40 mV/s, the electric capacitance of some samples was lower than that of the initial carbon nanotubes. For samples containing non-ozonized multiwalled nanotubes, the highest capacitance was observed for materials obtained at 80 °C; for ozonized samples, the optimum synthesis temperature was 60 °C. For optimized composition and conditions for the preparation of samples, the specific electric capacitance in asymmetric cells exceeds the specific electric capacitance of the electrodes based on the initial matrices by a factor of 1.5-2.9. Using the methods of galvanostatic charge-discharge and impedancemetry, it was established that electrochemical cells with nanocomposite electrodes have a higher capacitance and low internal resistance. It was discovered that sonication of the reaction medium during the preparation of nanocomposites leads to deterioration in the electrical capacity characteristics and to a noticeable increase in the internal resistance of the cells, especially the active component of the impedance.