Search

The present paper describes the prospects of using various graphene-like nanostructures as supercapacitor electrode materials. The studies were conducted in two stages. At the first stage, comparative potentiometric tests were performed with pristine (nonmodified) and polyaniline-modified graphene-based nanomaterials and activated carbon (as reference electrode material) in the inorganic electrolyte - 30 % H2SO4. The specific capacitance of the pristine nanostructure was 1.5-1.9 times higher than that of the other materials. At the second stage, the effect of the morphology of samples of this nonmodified material (activated under different conditions: time 2 and 3.5 h, and temperature 700, 750 and 800 °C) on the electrical characteristics of the supercapacitor was investigated in the aqueous and organic electrolytes using cyclic voltammetry and impedancemetry. In the organic electrolyte - 1 M tetraethylammonium tetrafluoroborate in acetonitrile, strong distortions of the cyclic current-voltage parameters were revealed when increasing the potential scan rate, which may be related to transport restrictions imposed on large organic ions. At the same time, in the aqueous electrolyte, the increase in the scan rate did not lead to any distortions, thereby implying effective ion transfer. However, additional testing of the electrode complex impedance confirmed the operational efficiency of the nanomaterials for intensive charge/discharge cycles in the organic electrolyte. Thus, establishing the possibility of adaptation of the morphological structure of the graphene-based nanomaterials for various electrolyte types to ensure the successful selection of an electrolyte for a corresponding graphene-based electrode was the most important result of these studies. [ABSTRACT FROM AUTHOR]

The present paper describes and compares the adsorption of heavy metal ions (Ni2+) on conventional and nanomodified AG-5 and NWC coconut shell-based activated carbons from aqueous solutions. The nanomodification of the materials was performed using "Taunit"-series carbon nanotubes (CNTs) obtained via chemical vapor deposition onto MgO-Al2O3 catalysts. The Ni2+ concentration in the solutions was determined spectrophotometrically. The efficiency of the Ni2+ adsorption was tested for all the materials. The adsorption mechanism was elucidated by adjusting the experimental data to the dual-site Langmuir-Freundlich (Sips) isotherm, which allowed confirming the existence of inner-sphere (higher-energy) and outer-sphere (lower-energy) sites on the adsorbent surface. For all the samples, the Ni2+ adsorption process was controlled mostly by the higher-energy sites. The results revealed that the nanomodification causes a 20 % increase in the adsorption capacity of the activated carbons at low initial and equilibrium Ni2+ concentrations, and a slight increase at higher concentrations. Thus, the CNTs-modified activated carbons can be used in water and wastewater treatment processes for efficiently removing heavy metal ions from aqueous media. [ABSTRACT FROM AUTHOR]