First Principles Study Of Van Der Waals Heterojunction Of Metal Sulfides

Constructing van der Waals（vdW）heterostructure is a effective route to modulate electronic properties for layered two-dimensional（2D）structures.2D metal sulfides,including Ⅲ-Ⅵ compounds（MX）and transition metal dichalcogenides（TMD）,have excellent electronic properties and show great potential in photovoltaic and spintronic devices.In this paper,we firstly construct the Type-Ⅱsemiconductor heterojunction based on MX and MX-Janus（XM₂X’/XM₂X）as an high-efficiency photocatalyst for water splitting reaction.Type-Ⅱheterojunction is useful for effectively separating electron-hole pairs and improving the photoelectric conversion efficiency（PCE）,which promotes the application of MX in water-splitting reaction.Secondly,the CrSe₂-Janus based vdW heterojunction（XCrX’|XCrX’）is constructed to modulate the critical distance of interlayer magnetic order transition by altering the strength of interlayer covalent-like quasi bonding（CLQB）,making a contribution to the reversible transition of interlayer magnetic ordering.1.Searching for high-efficiency photocatalysts is key to produce renewable hydrogen.Constructing heterojunction is a promising strategy for enhancing catalytic efficiency.Based on the first-principles calculations within HSE06 hybrid functional,we find vdW heterojunctions constructed by In Seand its Janus SeGa₂Te（SeGa₂Te/SeIn₂Se）are promising solar-driven water-splitting photocatalysts.Direct band gaps（1.74 e V）,and large optical absorbance（13.7%）promote sunlight absorption and electron-hole pair generation.The type-II band alignment and high PCE（20.2%）guarantee separation of photogenerated electron-hole pairs and utilization of solar power.Band edges,straddling and close to the redox potential of water splitting reaction can efficiently drive the HER and OER in both ph=0 and ph=7.Furthermore,outstanding photocatalytic properties are robust under vertical and in-plane strains,guaranteeing the application under actual experimental environment.2.Recently,the distance-dependent interlayer magnetism transition from antiferromagnetic（AFM）to ferromagnetic（FM）was found in many 2D ferromagnetic bilayers.Effective control of critical distance is a key point for reversible AFM-FM transition.We find that the charge transfer induced by elemental substitution of anionic layer can modulate the critical distance in SCrSe-based vdW bilayer structures using first-principles calculations.The interlayer AFM-FM transition is dependent on the interlayer p_zoverlap which is determined by the bonding strength（ΔE_b）of the CLQB from coupling of the interlayer p_zorbitals.Large critical distance is achieved when theΔE_bis significant in the bilayers.The interlayer p_zoverlap is altered by inducing intralayer of interlayer charge transfer,modulating the critical distance of interlayer AFM-FM transition.