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Abstract
<p class="first" id="d2974991e69">Development of applications for graphene are currently
hampered by its poor dispersion
in common, low boiling point solvents. Covalent functionalization is considered as
one method for addressing this challenge. To date, approaches have tended to focus
upon producing the graphene and functionalizing subsequently. Herein, we describe
simultaneous electrochemical exfoliation and functionalization of graphite using diazonium
salts at a single applied potential for the first time. Such an approach is advantageous,
compared to postfunctionalization of premade graphene, as both functionalization and
exfoliation occur at the same time, meaning that monolayer or few-layer graphene can
be functionalized and stabilized in situ before they aggregate. Furthermore, the N2
generated during in situ diazonium reduction is found to aid the separation of functionalized
graphene sheets. The degree of graphene functionalization was controlled by varying
the concentration of the diazonium species in the exfoliation solution. The formation
of functionalized graphene was confirmed using Raman spectroscopy, scanning electron
microscopy, transmission electron microscopy, atomic force microscopy, and X-ray photoelectron
spectroscopy. The functionalized graphene was soluble in aqueous systems, and its
solubility was 2 orders of magnitude higher than the nonfunctionalized electrochemically
exfoliated graphene sheets. Moreover, the functionalization enhanced the charge storage
capacity when used as an electrode in supercapacitor devices with the specific capacitance
being highly dependent on the degree of graphene functionalization. This simple method
of in situ simultaneous exfoliation and functionaliztion may aid the processing of
graphene for various applications.
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