The molecular functionalization
of two-dimensional MoS
2
is of practical relevance with
a view to, for example, facilitating
its liquid-phase processing or enhancing its performance in target
applications. While derivatization of metallic 1T-phase MoS
2
nanosheets has been relatively well studied, progress involving
their thermodynamically stable, 2H-phase counterpart has been more
limited due to the lower chemical reactivity of the latter. Here,
we report a simple electrolytic strategy to functionalize 2H-phase
MoS
2
nanosheets with molecular groups derived from organoiodides.
Upon cathodic treatment of a pre-expanded MoS
2
crystal
in an electrolyte containing the organoiodide, water-dispersible nanosheets
derivatized with acetic acid or aniline moieties (∼0.10 molecular
groups inserted per surface sulfur atom) were obtained. Analysis of
the functionalization process indicated it to be enabled by the external
supply of electrons from the cathodic potential, although they could
also be sourced from a proper reducing agent, as well as by the presence
of intrinsic defects in the 2H-phase MoS
2
lattice (e.g.,
sulfur vacancies), where the molecular groups can bind. The acetic
acid-functionalized nanosheets were tested as a non-noble metal-based
catalyst for nitroarene and organic dye reduction, which is of practical
utility in environmental remediation and chemical synthesis, and exhibited
a markedly enhanced activity, surpassing that of other (1T- or 2H-phase)
MoS
2
materials and most non-noble metal catalysts previously
reported for this application. The reduction kinetics (reaction order)
was seen to correlate with the net electric charge of the nitroarene/dye
molecules, which was ascribed to the distinct abilities of the latter
to diffuse to the catalyst surface. The functionalized MoS
2
catalyst also worked efficiently at realistic (i.e., high) reactant
concentrations, as well as with binary and ternary mixtures of the
reactants, and could be immobilized on a polymeric scaffold to expedite
its manipulation and reuse.
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