Microporous activated carbons from ammoxidised anthracite and their capacitance behaviours

The paper presents results of a study on obtaining N-enriched active carbons from anthracite mined in Siberia, and on its use as electrode material in supercapacitors. The anthracite was carbonised, activated with KOH and ammoxidised by a mixture of ammonia and air at the ratio 1:3 at 300 or 350 °C, at each stage of the activate production. The products were microporous N-enriched active carbon samples of well-developed surface area reaching from 1255 m2/g to 2011 m2/g and containing from 0.3 to 5.4 wt% of nitrogen. Capacity curves characteristics of the ammoxidised active carbon samples were determined by the galvanostatic and potentiodynamic methods, and by impedance spectroscopy for acidic and basic electrolyte solutions. The best capacity parameters in an acidic medium were obtained for the coal samples ammoxidised at the precursor stage (191 F/g), containing about 0.4 wt% of nitrogen, while in a basic medium—for the coal samples ammoxidised at the stage of active carbon (200 F/g), containing 4.0 wt% of nitrogen.