Two-dimensional (2D) materials have attracted numerous investigations after the discovery of graphene.

Possessing long-range FM order and tunable interlayer magnetic coupling, extensive investigations of monolayered ferromagnetic chromium triiodide (CrI 3 ) have been developed. In this work, by means of first-principles simulation, we systematically calculated the electronic and magnetic characteristic of two-dimensional (2D) CrI 3 adsorbed by gas molecules, CO, H 2 , H 2 O and N 2 , which can provide theoretical guidance to modulate the desired properties of this layered material. The results show that the adsorption of those gas molecules can significantly enhance FM couplings of monolayer CrI 3 . In particular, the N 2 adsorption can remarkably improve the Curie temperatures of the pristine CrI 3 monolayer by about 2.6 times. We also hope that our findings can provide more interest around the recently studied 2D FM semiconductors.

In this paper, the optical and electronic properties of WSSe/BSe heterostructure are investigated by first-principles calculations. The most stable stacking pattern of the WSSe/BSe compounds is formed by van der Waals interaction with a thermal stability proved by ab initio molecular dynamics simulation. The WSSe/BSe heterostructure exhibits a type-I band alignment with direct bandgap of 2.151 eV, which can improve the effective recombination of photoexcited holes and electrons. Furthermore, the band alignment of the WSSe/BSe heterostructure can straddle the water redox potential at pH 0–8, and it has a wide absorption range for visible light. In particular, the solar-to-hydrogen efficiency of the WSSe/BSe heterostructure is obtained at as high as 44.9% at pH 4 and 5. All these investigations show that the WSSe/BSe heterostructure has potential application in photocatalysts to decompose water.

Recently, a two-dimensional (2D) heterostructure has been widely investigated as a photocatalyst to decompose water using the extraordinary type-II band structure. In this work, the MoTe2/PtS2 van der Waals heterostructure (vdWH) is constructed with different stacking structures. Based on density functional calculations, the stacking-dependent electronic characteristic is explored, so that the MoTe2/PtS2 vdWH possesses type-I and type-II band structures for the light-emitting device and photocatalyst, respectively, with decent stacking configurations. The band alignment of the MoTe2/PtS2 vdWH is also addressed to obtain suitable band edge positions for water-splitting at pH 0. Furthermore, the potential drop is investigated, resulting from charge transfer between the MoTe2 and PtS2, which is another critical promotion to prevent the recombination of the photogenerated charges. Additionally, the MoTe2/PtS2 vdWH also demonstrates a novel and excellent optical absorption capacity in the visible wavelength range. Our work suggests a theoretical guide to designing and tuning the 2D heterostructure using photocatalytic and photovoltaic devices.

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