Strain engineering of the electro-optical and photocatalytic properties of single-layered Janus MoSSe: First principles calculations

In present work, we study the electronic, optical and photocatalytic properties of strained MoSSe monolayer through first-principles study. A single layer Janus MoSSe possesses a semiconducting character with a direct band gap of 1.59/2.09 eV obtained by PBE/HSE06 method. The valence band maximum (VBM) of Janus MoSSe monolayer is mainly contributed by the S-p orbital, whereas the conduction band minimum (CBM) comes from the Mo-d_x². Furthermore, Janus MoSSe monolayer has been proved to be energetically stable with no imaginary frequency in its phonon spectrum. Interesting, both the tensile and compressive strains can transform Janus MoSSe monolayer from direct to indirect band gap nature as well as tune its band gap. The compressive strain tends to an increase in the band gap, whereas the tensile strain leads to decrease in the band gap. Optical absorption of Janus MoSSe monolayer demonstrates that the tensile strain gives rise to an existence of blue shift, while compressive strain is responsible for the formation of a red shift. Photocatalytic properties show that Janus MoSSe monolayer with 4% or 6% strained could be a catalyst for the H₂O oxidation, making it suitable for water splitting applications.