The results seem to conclude that the binding energy of the C 1s peak for sp 3C is higher than that of sp 2C without any question. (13, 16, 17, 19-32) All of these studies assigned the peak for sp 3C in C 1s spectra as being higher than that for sp 2C ( Figure 1a and Table S1). (12) Similarly, a number of studies have used the difference of C 1s shift between sp 2C and sp 3C for their assignments. proposed a method to clarify the difference between sp 2C and sp 3C based on the difference of C 1s shifts between diamond and graphite in 1996. (10) Jackson and Nuzzo used this assignment to determine the areal ratio of sp 2C and sp 3C in 1995. (9) Lascovich and Scaglione differentiated the peaks of sp 2C and sp 3C in 1994. The history of XPS analysis for carbon materials with sp 3C and sp 2C has been summarized by Chu and Li. (39) Thus, assignments of C 1s spectra are still under debate. (4-7) Especially, X-ray photoelectron spectroscopy (XPS) has been well-known to be among the most powerful tools to determine the structures of carbon materials, (8-38) but the structures are extremely complicated because carbon materials contain various defects such as edges, functional groups, pentagons, heptagons, and sp 3C. (1-3) Many researchers have analyzed carbon materials using various techniques to clarify the difference of those structures at atomic scale. Carbon materials such as graphene, carbon nanotube, carbon fibers, and activated carbon materials have been intensively studied especially in the past few decades.

Xps peak