Understanding the nature of graphene oxide functional groups by modulation of the electrochemical reduction: a combined experimental and theoretical approach

Oxygen functional groups (OFGs) in graphene oxide (GO) are responsible for its different properties and peculiar reactivity in water and different solvents. A detailed assignment, both theoretical and experimental, of OFGs is still missing, and a full reconstruction of GO electrochemical behavior remains unreached. The spatial localization of OFGs is expected to play an important role in the reduction process, but so far, this important aspect remains undisclosed in the literature. Here, the nature and interactions of adjacent OFGs have been investigated, shedding light on the energetics of their electrochemical reduction. GO chemical modifications upon modulated and controlled electrochemical reduction conditions have been studied, in order to excite and reveal the contribution from single reactive OFGs. The characterization has been conducted via X-ray photoelectron spectroscopic analysis supported by theoretical modelling, to compose a detailed picture of the various local environments participating to the rich chemistry of GO. As a result, the interplay between XPS, cyclic voltammetry and DFT computation allowed for a consistent parallel assessment of both the C 1s ionization energy and the electrochemical reduction potential of the various carbonaceous species of GO.