An efficient GaS/ XTe2 (X=W, Mo) vdW heterstructure photocatalyst for water splitting: The first-principles study

In this paper, the electrical and optical properties of GaS/MoTe2 and GaS/WTe2 van der Waals heterostructure are investigated by first-principles methods, and their properties are modulated by applying biaxial strain and doping. It was revealed that the unstrained GaS/MoTe2 and GaS/WTe2 van der Waals heterostructures is semiconducting with an indirect bandgap of 1.16 eV and 1.28 eV using PBE methods, and the direction of the built-in electric field of the heterojunction is XTe2 pointing to GaS, which is perfect for powerful light absorption. The bandgap widths of the two heterostructure are significantly reduced compared with that of monolayer materials. Besides, the results show that the biaxial strain is an effective tool for adjusting the energy gap where the indirect energy gap under the strain effects ranged within a range of 0.33/0.34 eV at −8% to 0.361/0.464 eV at 6%. At −8% compressive strain, the interfacial charge transfer reaches a maximum for each of the two heterostructure. In addition the absorption coefficients of GaS/MoTe2 and GaS/WTe2 heterostructure increase in the visible and infrared regions and the absorption spectral range is broadened. Therefore, GaS/MoTe2 and GaS/WTe2 vdW heterostructure can be applied in photocatalytic water decomposition and other fields.