In Depth Investigations of Graphene Oxide Reduction via In Situ TEM Measurements

Graphene oxide (GO) strongly attracts research interest due to its use as precursor material for graphene-based material and its high flexibility in terms of functional modification offering promising applications in numerous fields [1-5]. Despite the efforts for investigating its atomic structure, which is critical for knowing its properties, several aspects remain unknown in particular the behavior of the physi-/chemi-sorbed and of the oxygen functional groups (OFGs) during GO reduction. Thus, here we present two different approaches for studying, in depth, the GO reduction via in-situ TEM investigations: thermal reduction and Joule heating. For achieving these comprehensive studies [7,8], we have performed high-resolution TEM (HRTEM) imaging and electron energy-loss spectroscopy (EELS) measurements and coupled (for the second of these studies) with electrical conductivity measurements. In both studies we have identified the transformations of different oxygen functional groups, the desorption of physisorbed and chemisorbed water and the graphitization of the GO flakes. These in-depth analyses provide a detailed roadmap of the behavior of GO during its reduction. All these findings improve the knowledge of this complex and heterogeneous material, which is crucial for the study of their physical and chemical properties and its future applications.<br/><br/><br/>[1] G. Eda, & M. Chhowalla, Advanced materials, 22, 2392 (2010).<br/>[2] K.P. Loh, Q. Bao, G. Eda, M. Chhowalla, Nature chemistry 2, 1015 (2010).<br/>[3] D.J, Nuñez, et al., Chem. Science (2016).<br/>[4] D. D’Angelo, et al. J. Phys. Chem. C, 121, 5408 (2017).<br/>[5] C. Backes, et al., 2D Mat.. 7, 022001 (2020).<br/>[6] M. Pelaez-Fernandez, A. Bermejo-Solis, A.M. Benito, W. Maser, R. Arenal, Carbon 78, 477 (2021).<br/>[7] S. Hettler, D. Sebastian, M. Pelaez-Fdez, A. Benito, W. Maser, R. Arenal, 2D Mat. 8, 031001 (2021).<br/>[8] RA acknowledges funding from the EU H2020 program “Graphene Flagship” (Grant Agreement 881603) and EU H2020 program “ESTEEM3” (Grant Agreement 823717). MICINN (project grants PID2019-104739GB-100/AEI/10.13039/501100011033 and PID2019-104272RB-C51/AEI/10.13039/501100011033) and Government of Aragon (projects DGA E13_20R and T03-20R) are also acknowledged.