Origin of the Large N 1s Binding Energy in X-ray Photoelectron Spectra of Calcined Carbonaceous Materials

Abstract

Theoretical models and ab initio Hartree-Fock wave functions are used to investigate the N 1s core level binding energies of N-containing calcined carbonaceous materials. Comparison of calculated and experimental values for a series of test molecules reveals that the N 1s core level shift from one compound to another is mainly originated by initial state effects. This permits a systematic study of different situations and allows establishment that three different types of nonoxidized N atoms can be present in these materials. These are "pyridinic", "pyrrolic", and "graphitic" nitrogen with binding energies of ≈399.0, ≈400.3, and ≈401-403 eV, respectively. This assignment is in very good agreement with a recent experimental X-ray photoelectron spectra on petroleum cokes and demonstrates, for the first time, that it is possible for N to exhibit rather large core level 1s energies without requiring the presence of any charge transfer from N-oxide groups. Theoretical reasons for such a behavior are also given.

High oxygen-reduction activity of silk-derived activated carbon

“…3) suggests that graphitization of the CS-ACs increased gradually with increasing heat-treatment temperature. The nitrogen atoms incorporated in CS-ACs were examined by X-ray photoelectron spectroscopy (XPS), because it has been suggested that various types of nitrogen atoms, including pyridine-like nitrogen (398.6 eV), pyrrole-like nitrogen (400.5 eV), quaternary nitrogen (401.3 eV), and oxide nitrogen (402-405 eV), are present in nitrogen-containing carbons [18][19][20][21][22]. As the heat-treatment temperature increased, the proportion of pyridine-like N species decreased, and almost disappeared in the case of CS1200-AC, whereas some quaternary nitrogen (401.3 eV) species remained even after heat-treatment at 1200 °C.…”

Organic nitrogen chemistry during low-grade metamorphism

“…• A pyridinic nitrogen atom substitutes for a carbon atom in an aromatic ring and is bonded to two carbon atoms. None of these two carbon atoms is bonded to atoms other than carbon or hydrogen; see Fig.2c (e.g., Pels et al, 1995;Casanovas et al, 1996) • Ammonium fixed in clay (see Fig. 6d, f).…”

“…• N-C3 as described for N-Q1 above (Casanovas et al, 1996) • Nitrogen oxide (Pels et al, 1995) • N-C3 as described for N-Q1 above (Casanovas et al, 1996) • A pyrrolic nitrogen atom substitutes for a carbon atom in a non-aromatic ring and is bonded to one hydrogen atom and two carbon atoms. None of these two carbon atoms is bonded to additional atoms other than carbon or hydrogen; see Fig.…”

“…None of these two carbon atoms is bonded to additional atoms other than carbon or hydrogen; see Fig. 2a (e.g., Pels et al, 1995;Casanovas et al, 1996).…”

“…6). Candidates for generating the N-Q2 sub-peak at 402.7 eV (FWHM = 1.5 eV) and the N-X sub-peak at 403.6 eV (FWHM = 1.5 eV) are (i) pyridinic nitrogen atoms bonded to oxygen atoms, (ii) nitrogen substituting for carbon in condensed, partially aromatic systems (a higher nitrogen binding energy would arise both from charge transfer and hybridization; Casanovas et al, 1996), and (iii) ammonium fixed in clays ( Fig. 5; Buckley et al, 1995Buckley et al, , 1996Gong et al, 1999) where the outermost sheet is composed of oxygen anions inducing a particular local interlayer environment, in contrast to simple ammonium salts (Yu, 2007;He et al, 2007).…”