Investigation of Stacking Effects of Bilayer MoSSe on Photocatalytic Water Splitting

Abstract

Stacking two-dimensional materials into a heterostructure, which is also known as van der Waals epitaxy, is an effective method to tune the properties of pristine monolayer structures. Recently, Janus monolayer MoSSe has been successfully fabricated in an experiment, which might be beneficial for photocatalytic water splitting due to the inner electric field caused by the breaking of the inversion symmetry. Considering that the bilayer structure has natural advantages over the monolayer structure in photocatalytic water splitting, we systematically investigate the six stacking configurations of the bilayer MoSSe. All these stacking configurations are stable according to their calculated formation energies. The stacking effect of the properties such as the band gap and charge distribution in the vertical direction are much stronger than those in the in-plane direction. Only the AB_SSe case has a direct band gap when spin–orbit coupling is considered. Moreover, AB_SSe is excellent material for photocatalytic water splitting also because of its high adsorption spectrum, suitable band edge position, and type II heterojunction. The direct band gap and type II heterojunction may be attributed to the broken strong inversion symmetry. Our work is helpful in understanding the mechanism of the stacking effect in the bilayer MoSSe and can promote the application of bilayer transition-metal dichalcogenides in photocatalytic water splitting.