Changes in the Surface Chemistry and Adsorptive Properties of Active Carbon Previously Oxidised and Heat-treated at Various Temperatures. II. Electrochemical Investigations of Surface Chemistry

摘要

Thermal treatment of oxidised active carbon under vacuum conditions led to changes in the chemical nature of its surface, e. g. a stepwise decrease in the total oxygen content and an increase in the pH of the carbon slurry. Annealing reducxed the number of surface oxygen-containing groups and increased the overall number of basic groups. The results of the cyclic voltammetric studies analysed in this paper clearly indicate only a weak relationship between the presence and number of cathodic/anodic peaks, i.e. reduction/oxidation of electroactive surface groups, forming during cyclisation and the degree of surface oxidation (regulated by heat treatment) of the carbon samples tested. The electrochemical behaviour of powdered carbon suggested electro-oxidation of the surface of the electrode material with participation of adsorbed hydroxy ions and water molecules. The possible electrochemical reactions and mechanisms of the surface processes were discussed in order to explain the observed phenomena.