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Oxidation of activated carbon (AC) with nitric acid was carried out, and the resulting AC/HNO 3 showed high capacity when used as supercapacitor electrode material operated in the KOH electrolyte. Oxidation caused different structural changes in the AC, reducing the specific surface area and the total pore volume. After oxidation, the content of all types of oxygen-containing groups and, especially, carboxyl groups showed a significant increase. Despite the significant reduction of the specific surface area, the specific capacitance of the oxidized AC in symmetric supercapacitor electrodes is 1.4 times larger than that for the pristine AC.

Bromination and oxidation are concurrent reactions that passed on the surface of carbon solids and carbon nanomaterials. In this study, their products were modeled for a hexagonal carbon network that forming a honeycomb 2D planar structure made of sp2-hybridized bonded carbon. Two types of active centers, namely, HC=CH and C-H groups linked to peripheral zigzag carbon atoms, were considered during the DFT simulations. The oxidation process is more advantageous than bromination. Free active centers, even that on the oxidized surface, maintain their ability to the bromine addition reaction. However, the probability of their existence on the oxidized surface is very low. The active centers of the surface can be renewed by the removal of oxygen-containing groups at thermal treatment in an inert atmosphere.