Relationship between Width and Height of π* Peak in C K-XANES of Graphitic Carbons

Abstract

The relationship between the width and height of the π* peak on X-ray absorption near edge structure (XANES) in the C K region of graphitic carbons is investigated from XANES measurements and theoretical analysis. This relationship is herein named the "characteristic diagram of π* peak profile". Mechanically ground (MG) graphite experimentally exhibits a linear correlation on the diagram. To understand the linear correlation, C K-XANES of the graphitic hexagonal carbon layers are calculated using first-principles calculations by focusing on the edge carbon atoms. The linear correlation is well explained by the ratio of the edge carbon atoms of the graphitic hexagonal carbon layers. The characteristic diagram of π* peak profile is applied to industrial carbon black (CB) for identification. CBs exhibit identical distributions on the diagram, which depend on their uses. It is therefore confirmed that the proposed characteristic diagram of π* peak profile can be a useful tool to identify graphitic carbons from the edge carbon atoms.

Elucidation of Surface Functional Groups Deposited by Electrochemical Surface Treatment of Discontinuous Carbon Fiber by NEXAFS and XPS

“…Based on modeling of zigzag and armchair edges, broader π* peaks or a shoulder leading the main peak by about 1 eV may be indicative of increased populations of edge carbon. 54 This does not appear to be the case in the spectra herein, suggesting that the total edge content of these treated fibers has not significantly changed. Lee et al identified a peak at 286.9 eV that was related to π* (C−O) for phenolic terminated basal planes.…”

“…They identified the (CC) 1s → π* peak at about 285.1 eV, and a (C–C) (1s → σ*) peak at about 292.5 eV. Based on modeling of zigzag and armchair edges, broader π* peaks or a shoulder leading the main peak by about 1 eV may be indicative of increased populations of edge carbon . This does not appear to be the case in the spectra herein, suggesting that the total edge content of these treated fibers has not significantly changed.…”