The structure of graphite oxide: Investigation of its surface chemical groups

TL;DR

This study comprehensively analyzes the surface chemical groups of graphite oxide using multiple advanced techniques, revealing its complex structure and proposing a new surface chemistry model.

Contribution

It provides a detailed, multi-technique investigation of GO's surface groups and introduces a novel structural model based on combined spectroscopic evidence.

Findings

GO contains amorphous and crystalline phases.

Surface groups include -O-, -OH, and -C=O.

The sp2/sp3 ratio decreases with preparation time.

Abstract

The structure of graphite oxide (GO) has been systematically studied using various tools such as SEM, TEM, XRD, Fourier transform infrared spectroscopy (FT-IR), X-ray photoemission spectroscopy (XPS), 13C solid state NMR, and O K-edge X-ray absorption near edge structure (XANES). The TEM data reveal that GO consists of amorphous and crystalline phases. The XPS data show that some carbon atoms have sp3 orbitals and others have sp2 orbitals. The ratio of sp2 to sp3 bonded carbon atoms decreases as sample preparation times increase. The 13C solid-state NMR spectra of GO indicate the existence of -OH and -O- groups for which peaks appear at 60 and 70 ppm, respectively. FT-IR results corroborate these findings. The existence of ketone groups is also implied by FT-IR, which is verified by O K-edge XANES and 13C solid-state NMR. We propose a new model for GO based on the results; -O-, -OH, and -C=O groups are on the surface.