Transition metal dichalcogenide (TMDC) monolayers exhibit
great
photocatalytic performances and tunabilities. By using first-principles
simulations based on density functional theory, we demonstrate here
that external electric bias can be employed to further improve the
photocatalytic hydrogen production efficiencies of the six AB2 (A = Mo, W and B = S, Se, Te) TMDC monolayers since these
are influenced by their piezoelectric response. In particular, when
subjected to a proper amount of electrically induced tensile biaxial
strain, most TMDC monolayers turn into potentially ideal photocatalysts
toward the hydrogen evolution reaction (HER). The beneficial effects
of introducing tensile biaxial strain on the TMDC monolayers are not
limited to the reduction of the band gap and proper adjustment of
the band edge positions; the concomitant hydrogen adsorption free
energies are also modified in such a way that the HER reaction is
noticeably favored.