X-ray Spectroscopy Fingerprints of Pristine and Functionalized Graphene.

Anja Aarva,Tomi Laurila,Sami Sainio,Miguel A Caro,Volker L Deringer

doi:10.1021/acs.jpcc.1c03238

Abstract

In this work, we demonstrate how to identify and characterize the atomic structure of pristine and functionalized graphene materials from a combination of computational simulation of X-ray spectra, on the one hand, and computer-aided interpretation of experimental spectra, on the other. Despite the enormous scientific and industrial interest, the precise structure of these 2D materials remains under debate. As we show in this study, a wide range of model structures from pristine to heavily oxidized graphene can be studied and understood with the same approach. We move systematically from pristine to highly oxidized and defective computational models, and we compare the simulation results with experimental data. Comparison with experiments is valuable also the other way around; this method allows us to verify that the simulated models are close to the real samples, which in turn makes simulated structures amenable to several computational experiments. Our results provide ab initio semiquantitative information and a new platform for extended insight into the structure and chemical composition of graphene-based materials.

Highlights

Graphene (G) and graphene oxide (GO) have attracted the attention of academic research as well as industry globally, in particular since 2010.1,2 Graphene-based materials are promising candidates for a vast variety of applications in several fields, such as biotechnology, nanoelectronics, solar cells, lithium-ion and sodium-ion batteries, supercapacitors, anticorrosion coating, and sensors, to name a few.[3]
We provide a computational methodology that extends on initial work in refs 10−13, as well as a comprehensive set of reference data, for interpreting experimental X-ray spectroscopy data of graphene-based compounds, aiming at careful structural and chemical characterization of these materials
Among the different X-ray spectroscopy techniques, we focus on X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS)

Summary

INTRODUCTION

Graphene (G) and graphene oxide (GO) have attracted the attention of academic research as well as industry globally, in particular since 2010.1,2 Graphene-based materials are promising candidates for a vast variety of applications in several fields, such as biotechnology, nanoelectronics, solar cells, lithium-ion and sodium-ion batteries, supercapacitors, anticorrosion coating, and sensors, to name a few.[3]. XAS and XPS are popular and accurate methods for analyzing the composition of materials in general.[14,15] XAS probes the allowed transitions from electronic core levels to conduction (unoccupied) states In other words, it provides detailed information about the structure of the material’s conduction band. We use a carefully selected ensemble of model structures, to represent the different existing types of graphene-based materials From these structures, we calculate their signature X-ray spectral responses from density functional theory (DFT). These calculated spectra can be compared with experimental spectra via computational fitting,[11] to estimate the type and composition of the experimental graphene/graphite sample in question In this way, we manage to provide a qualitative and quantitative means to characterize the range of atomic structures present in G- and GO-based materials

COMPUTATIONAL AND EXPERIMENTAL PROTOCOLS

RESULTS AND DISCUSSION

CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES