Layered transition-metal
dichalcogenides (LTMDs) in two-dimensional
(2D) form are attractive for electrochemical energy storage, but research
efforts in this realm have so far largely focused on the best-known
members of such a family of materials, mainly MoS2, MoSe2, and WS2. To exploit the potential of further,
currently less-studied 2D LTMDs, targeted methods for their production,
preferably by cost-effective and sustainable means, as well as control
over their nanomorphology, are highly desirable. Here, we report a
quick and straightforward route for the preparation of 2D NbSe2and other metallic 2D LTMDs that relies on delaminating their
bulk parent solid under aqueous cathodic conditions. Unlike typical
electrochemical exfoliation methods for 2D materials, which generally
require an additional processing step (e.g., sonication) to complete
delamination, the present electrolytic strategy yielded directly exfoliated
nano-objects in a very short time (1–2 min) and with significant
yields (∼16 wt %). Moreover, the dominant morphology of the
exfoliated 2D NbSe2products could be tuned between rolled-up
nanosheets (nanorolls) and unfolded nanosheets, depending on the solvent
where the nano-objects were dispersed (water or isopropanol). This
rather unusual delamination behavior of NbSe2was explored
and concluded to occur via a redox mechanism that involves some degree
of hydrolytic oxidation of the material triggered by the cathodic
treatment. The delamination strategy could be extended to other metallic
LTMDs, such as NbS2and VSe2. When tested toward
electrochemical lithium storage, electrodes based on the exfoliated
NbSe2products delivered very high capacity values, up
to 750–800 mA h g–1at 0.5 A g–1, where the positive effect of the nanoroll morphology, associated
to increased accessibility of the lithium storage sites, was made
apparent. Overall, these results are expected to expand the availability
of fit-for-purpose 2D LTMDs by resorting to simple and expeditious
production strategies of low environmental impact.