Martin Jindra^1;2, Matěj Velický¹, Martin Kalbáč¹, Otakar Frank^1
1 J. Heyrovsky Institute of Physical Chemistry, Czech Academy of Sciences, 182 23 Prague, Czech Republic
² Department of Physical Chemistry, University of Chemistry and Technology, 166 28 Prague, Czech Republic

In-situ combination of Raman spectroscopy and electrochemistry localized into a small droplet of an electrolyte is an ideal method for the measurement of charge-transfer processes in 2D materials. Our microdroplet spectroelectrochemistry (µ-SEC) setup allows us to perform these measurements on the basal plane of exfoliated graphene monolayers without the inence of any surface contamination, flake edges and/or monolayer/multilayer interfaces.
Influence of structural defects on the spectroelectrochemical and electrochemical behaviour of monolayer graphene is discussed in this work. Our µ-SEC technique highlights the importance of defects on graphene charge-transfer processes. We observed splitting of the Raman G band of graphene, which was caused by defect formation in the crystal structure of graphene and thus differently doped areas with different charge-transfer kinetics. We also show the evaluation of the heterogenous electron transfer coefficient of a redox reaction between graphene and an electrochemical outer-sphere mediator with two distinct rates for pristine and defective areas [1].
[1] Jindra et al., J. Phys. Chem. Lett. 2022, 13(2), 642-648.