  The experimental exfoliation of layered group-IV monochalcogenides
--semiconductors isostructural to black phosphorus-- using processes similar to
those followed in the production of graphene or phosphorene has turned out
unsuccessful thus far, as if the chemical degradation observed in black
phosphorus was aggravated in these monochalcogenides. Here, we document a
facile dissociation of water by these materials within ten nanoseconds from
room-temperature Car-Parrinello molecular dynamics calculations under standard
temperature and pressure conditions. These results suggest that humidity must
be fully eradicated to exfoliate monolayers successfully, for instance, by
placing samples in a hydrophobic solution during mechanical exfoliation. From
another materials perspective, these two-dimensional materials that create
individual hydrogen ions out of water without illumination may become relevant
for applications in hydrogen production and storage.
