Ammoxidation of active carbons for improvement of supercapacitor characteristics

Modification of active carbon by ammoxidation was used to obtain electrode material with intermediate acidic-basic properties. It allowed advantage to be taken of the pseudocapacitance characteristics of the material for the improvement of the supercapacitor. Precursor fabric from regenerated cellulose was subjected to carbonization, followed by steam activation at 400 and 800 °C, respectively. Ammoxidation was carried out with a mixture of ammonia and air at a ratio of 1:3 in a flow reactor at 250 °C at different stages of the process, i.e. before or after carbonization, or after activation. Active materials were described with respect to microporous structure (nitrogen adsorption), chemical composition (elemental analysis and XPS) and investigated by electrochemical methods (cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy) in acidic (4 M H₂SO₄) and alkaline (7 M KOH) media. The electrochemical behavior of individual samples is discussed from the viewpoint of the diverse electron-donor properties of the functional groups of both nitrogen and oxygen heteroatoms which result from different technological processing conditions.