Exploring the Role of Molecular Intercalants in Electrochemical Production of Graphene-Based 2D Materials

Abstract

Since the discovery of graphene, two-dimensional (2D) materials have gained extensive attention due to the unique material properties from their reduced dimensionality. Numerous techniques have been thoroughly investigated for the fabrication of graphene-based 2D materials. Among them, electrochemical synthesis is one of the most promising approaches for the large-scale production of 2D materials with tunable properties [1-3]. Especially, intercalation of various ions/molecules electrochemically driven in between the graphene sheets plays the key role in the synthesis of single or few-layer 2D materials. However, the influence of molecular intercalants is still poorly understood.In this work, we studied different types of intercalants (i.e., ClO4 -, PF6 -, BF4-, HSO4 -) and explored the inserting process of molecular anions in-between the weekly-bonded layered materials driven by electrochemistry. Combining the cyclic voltammetry, XRD, Raman and density functional theory computation modeling, we can monitor the intercalation behavior of different anions and evaluate the contribution of intercalants in the high-yield production of graphene by electrochemical exfoliation. By optimizing the use of certain molecular intercalants, high exfoliation yield (>80 %) of graphene nanosheets with moderate oxidation damage and good electrochemical stability was achieved assisted by electrochemical exfoliation. Our study provides new insights into the electrochemical production of graphene-based 2D materials and suggests that the introduction of molecular intercalants is a promising tool for the controlled synthesis of layered 2D materials.Reference:(1) Xia, Z. Y.; Pezzini, S.; Treossi, E.; Giambastiani, G.; Corticelli, F.; Morandi, V.; Zanelli, A.; Bellani, V.; Palermo, V. The Exfoliation of Graphene in Liquids by Electrochemical, Chemical, and Sonication-Assisted Techniques: A Nanoscale Study. Advanced Functional Materials 2013, 23 (37), 4684-4693. DOI: 10.1002/adfm.201203686.(2) Xia, Z. Y.; Maccaferri, G.; Zanardi, C.; Christian, M.; Ortolani, L.; Morandi, V.; Bellani, V.; Kovtun, A.; Dell'Elce, S.; Candini, A.; et al. Dispersion Stability and Surface Morphology Study of Electrochemically Exfoliated Bilayer Graphene Oxide. Journal of Physical Chemistry C 2019, 123 (24), 15122-15130. DOI: 10.1021/acs.jpcc.9b03395.(3) Cao, J. Y.; He, P.; Mohammed, M. A.; Zhao, X.; Young, R. J.; Derby, B.; Kinloch, I. A.; Dryfe, R. A. W. Two-Step Electrochemical Intercalation and Oxidation of Graphite for the Mass Production of Graphene Oxide. Journal of the American Chemical Society 2017, 139 (48), 17446-17456. DOI: 10.1021/jacs.7b08515.