X-ray Photoelectron Spectroscopy Study of Nitrogen-Enriched Active Carbons Obtained by Ammoxidation and Chemical Activation of Brown and Bituminous Coals

Abstract

The study reported has been undertaken to characterize the changes taking place on the surface of the nitrogen-enriched active carbons. The method applied for this purpose was X-ray photoelectron spectroscopy (XPS), and the samples studied were active carbons prepared from Polish brown and bituminous coals. An ammonia−air mixture was applied as a reagent introducing nitrogen functions into the carbon structure. Nitrogen was introduced both to demineralized coals and to active carbons obtained by carbonization and chemical activation of nonmodified precursors. The activation was performed at 700 °C with KOH, in an argon atmosphere. Results of XPS measurements have shown that in the active carbons enriched in nitrogen at the stage of precursor the dominant nitrogen species are the N-5 and N-6 groups; while in the samples ammoxidized after chemical activation, the dominant nitrogen species are the surface groups of imines, amines, amides and nitriles, accompanied by lactams and N-5 and N-6 groups.