Designing New Two-Dimensional Janus Nanomaterials by Anionic Exchange

Two-dimensional nanomaterials have played a key role in the recent advances in nanoscience for a decade, especially in the area of energy technology. Of late, a new class of 2D material has been suggested and experimentally realized – namely, the Janus monolayer. Different from preceding 2D materials, such as graphene and transition metal dichalcogenides, Janus monolayers lack the inversion symmetry in both in-plane and out-of-plane directions, and this leads to new anisotropic physiochemical properties which can be potentially useful for key energy applications. In this work, we design and investigate various novel two-dimensional Janus materials, via the anionic exchange method. In particular, by starting from the well-known MoS₂ and WS₂ monolayers, we substitute the top and bottom sulfur layers using a combination of group V and VII anions. Density-functional theory calculations are then performed to examine their anisotropic material properties.